EXCHANGE 


The  Preparation  and  Decomposition  of 
Tetrathionates 


DISSERTATION 


PRESENTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIRE- 
MENTS FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 
IN  THE  GRADUATE  SCHOOL  OF  THE  OHIO 
STATE  UNIVERSITY 


BY 


WALTER  SCOTT 


THE  OHIO  STATE  UNIVERSITY 
1920 


The  Preparation  and  Decomposition  of 
Tetrathionates 


DISSERTATION 

PRESENTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIRE- 
MENTS FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 
IN  THE  GRADUATE  SCHOOL  OF  THE  OHIO 
STATE  UNIVERSITY 


BY 


WALTER  SCOTT 


THE  OHIO  STATE  UNIVERSITY 
1920 


**< 


TABLE  OF  CONTENTS 
Sodium  Tetrathionate : 

Bibliography.  Preparation,  (I)  Method  of  Klobukow  Modified;  (II)  Method  of 
Sander.  Analysis  for  Sulphur  When  Precipitated  by  Addition  of  Absolute  Alcohol. 
Qualitative  Tests.  Comparative  Analyses  for  Purity.  Determination  of  Water  of 
Crystallization.  Behavior  of  Hydrous  Salt  When  Exposed  to  Air  Under  Certain  Con- 
ditions. Suggested  Method  for  Preparation. 

Barium  Tetrathionate:  • 

Bibliography.  Preparation,  (I)  Previous  Methods  Used;  (II)  General  Procedure 
of  Method  Used;  (III)  Preparation  of  Barium  Thiosulphate;  (IV)  Difficulties  En- 
countered. Comparative  Analyses  for  Purity.  Water  of  Crystallization.  Behavior 
of  the  Hydrous  Salt  when  Exposed  to  Air.  Suggested  Method  for  Preparation. 
Qualitative  Decomposition.  Quantitative  Decomposition,  (I)  Preliminary;  (II)  De- 
scription of  Apparatus;  (III)  Procedure;  (IV)  Purification  of  Bromine;  (V)  Prepara- 
tion of  Sodium  Hypobromite;  (VI)  Blank  Experiment;  (VII)  Results  in  Table  XI. 
Quantitative  Decomposition  Including  the  Analysis  of  the  Filtrate. 

Crystallographic  Study  of  Sodium  and  Barium  Tetrathionates : 

Bibliography.  Experimental,  (I)  Sodium  Tetrathionate,  (II)  Barium  Tetra- 
thionate. 

Zinc   Tetrathionate: 

Bibliography.  Preparation,  (I)  Previous  Methods  Used;  (II)  General  Procedure 
of  Method  Used;  (III)  Preparation  of  Barium  Tetrathionate;  (IV)  Preparation  of  Zinc 
Sulphate.  Qualitative  Decomposition.  Quantitative  Decomposition,  (I)  Descriptive; 
(II)  Procedure.  Quantitative  Decomposition  Including  the  Analysis  of  the  Filtrate. 

Nickel  Tetrathionate: 

Bibliography.  Preparation,  (I)  General  Procedure  of  the  Method  Used;  (II) 
The  barium  tetrathionate  and  Nickel  Sulphate  Used.  Qualitative  Decomposition. 


INTRODUCTION 

Tetrathionates  and  tetrathionic  acid  were  first  prepared  by  Fordos 
and  Gelis  in  1842.  They  were  making  anaylses  of  a  great  number  of 
commercial  salts,  then  called  "hyposulphites,"  in  order  to  see  if  they  had 
the  same  composition. 

In  the  course  of  the  analysis  they  attempted  to  oxidize  a  solution  of  the 
salts  with  iodine  in  order  to  convert  the  sulphur  to  sulphate.  Instead  of 
forming  a  sulphate,  a  new  compound  of  sulphur  was  formed  and  which 
proved  on  analysis  to  have  the  general  formula  M//S4Oe.  Since  the  dis- 
covery of  the  tetrathionates  much  work  has  been  done  on  them  and  the 
results  obtained  are  not  in  agreement.  The  principal  reason  for  this 
seems  to  be  that  the  tetrathionates  were  prepared  from  Wackenroder' s 
solution,  which  was  not  of  uniform  composition. 

The  object  of  the  present  investigation  was  to  get  some  definite  data 
on  some  of  the  tetrathionates,  and  to  further  study  their  decomposition 
quantitatively  under  the  same  conditions. 

SODIUM  TETRATHIONATE 

BIBLIOGRAPHY 

Fordos  and  Gelis,  Ann.  Chim.  phys.,  (3)  6,  486,  (1842). 
Jour.  f.  prak.  Chem.,  28,  473,  (1843). 
Compt.  rend.,  2,  920,  (1843). 

Sodium  tetrathionate  was  prepared  by  the  action  of  sodium  thiosulphate  on  iodine. 
The  sodium  thiosulphate  was  dissolved  in  water  and  the  iodine  added  a  little  at  a  time 
until  there  was  a  slight  iodine  color  remaining.  They  also  stated  "That  the  liquid 
contained  neither  sulphates,  sulphuric  acid  nor  any  salt  which  is  precipitated  by  baryta." 
Fordos  and  Gelis,  Ann.  chim.  phys.,  (3)  8,  351,  (1843). 

Sodium  tetrathionate  was  prepared  by  the  action  of  ferric  chloride  on  sodium 
thiosulphate. 

2Na2So03  +  2FeCl3  =  2FeCl2  +  2NaCl  +  Na2S4O6 

All  ferric  salts  behave  in  a  similar  way. 
Fordos  and  Gelis,  Ann.  chim.  phys.,  (3)  13,  402,  (1845). 

Sodium  tetrathionate  was  prepared  by  the  action  of  auric  chloride  on  sodium 
thiosulphate. 

Kessler,  Jour.  f.  prak.  Chem.,  47,  34,  (1849). 

Pogg.  Ann.  Phys.  Chem.  74,  255,  (1849). 
Sodium  tetrathionate  was  prepared  by  adding  cupric  chloride  dropwise  to  a  con- 


6 

centrated  solution  of  sodium  thiosulphate  until  the  cuprous  chloride  had  separated 
and  the  solution  had  a  light  blue  color.  It  was  filtered,  and  alcohol  added  to  the  filtrate 
whereby  the  sodium  tetrathionate  was  precipitated. 

Kressler  also  prepared  the  salt  by  two  other  methods. 

(a)  By  the  addition  of  an  equivalent  amount  of  sodium  carbonate  to  a  solution  of 
tetrathionic  acid,  and  then  adding  alcohol. 

(6)  By  mixing  equivalent  solutions  of  sodium  sulphate  and  lead  tetrathionate, 
filtering  and  then  adding  alcohol. 

The  tetrathionic  acid  and  lead  tetrathionate  were  prepared  by  the  method  of  Fordos 
and  Gelis.  (loc.  cit.) 

Sonstadt,  Chem.  News,  26,  99  (1872). 

Sodium  tetrathionate  was  prepared  by  mixing  solutions  of  sodium  thiosulphate 
and  potassium  iodate  and  then  adding  hydrochloric  acid. 

6Na2S2O3  +  KIO3  +  6HC1  =  3Na2S4O6  +  KI  +  GNaCl  +  3H,O 

Citric  and  tartaric  acids  were  used  instead  of  hydrochloric  and  similar  results  were 
obtained. 

Sonstadt  suggests  the  use  of  pure  sodium  thiosulphate  to  determine  pure  iodine,  as 
pure  iodine  will  not  liberate  any  sulphur  from  pure  thiosulphate  solution. 

Lunge,  Ber.,  12,  404,   (1879). 

In  experimenting  with  the  action  of  hypochlorite  on  thiosulphate,  having  the 
thiosulphate  in  excess,  the  principal  reaction  was  found  to  be 
2Na2S2O3  +  C12  =  Na2S4O6  +  2NaCl 

Other  reactions  occur. 

Klobukow,  Ber.,  18,  1871,  (1885). 

Sodium  tetrathionate  was  prepared  by  the  action  of  iodine  on  sodium  thiosulphate. 
The  sodium  thiosulphate  was  finely  pulverized  in  a  mortar  and  a  small  amount  of  water 
added  to  make  a  paste.  Finely  pulverized  iodine  was  added  a  little  at  a  time,  grinding 
thoroughly  after  each  addition,  until  the  iodine  was  in  slight  excess  which  may  be  told 
by  the  appearance  of  the  yellow  color.  Pour  the  syrupy  liquid  into  a  beaker  and  add 
alcohol,  whereupon  the  tetrathionate  salt  is  immediately  precipitated  as  a  snow-white 
crystalline  precipitate.  In  case  the  iodine  color  disappears  during  the  grinding,  a  little 
more  iodine  should  be  added  until  there  is  a  permanent  iodine  color  remaining.  By 
working  under  the  above  conditions  they  believe  there  was  not  an  excess  of  alkali  thio- 
sulphate present,  nor  did  any  decomposition  occur  liberating  sulphur  dioxide.  After 
two  or  three  hours  standing,  the  mixture  was  filtered  and  the  precipitate  washed  with 
alcohol  until  all  the  iodine  and  iodide  had  been  removed.  The  precipitate  was  dis- 
solved in  lukewarm  water,  reprecipitated  by  the  addition  of  alcohol,  filtered,  and  placed 
in  a  vacuum  desiccator  over  sulphuric  acid  to  dry. 

Villiers,  Compt.  rend.,  108,  402-03,  (1889). 

Ber.,  22,  R.  222,  (1889). 

Sodium  tetrathionate  was  prepared  by  passing  sulphur  dioxide  through  a  solution 
of  sodium  thiosulphate. 


4-  3SO,  =  Na2S4O6  +  Na2S3O6 

Norris  and  Fay,  Amer.  Chem.  Journ.,  18,  703,  (1896). 

Hydrochloric  acid  was  added  to  a  solution  of  selenious  acid,  and  then  an  excess 
of  sodium  thiosulphate.  The  excess  of  sodium  thiosulphate  was  taken  up  with  iodine. 
SeO2  +  4Na2S2O3  =  2Na2S4O6  +  Se  +  2Na2O 

The  reaction  is  quantitative. 

Nabl,  Ber.,  33,  3554,  (1900). 

Sodium  tetrathionate  was  prepared  by  the  action  of  hydrogen  peroxide  on  a  solu- 
tion of  sodium  thiosulphate. 

2Na2S203  +  H202  =  Na2S4O6  +  2NaOH 

The  sodium  hydroxide  must  be  removed  as  soon  as  it  is  formed  or  there  is  also  formed 
in  the  solution,  sulphite,  thiosulphate  and  sulphate. 

He  withdraws  his  previous  statement  as  to  the  action  of  hydrogen  peroxide  on  a 
solution  of  sodium  thiosulphate.  Ber.,  33,  3093,  (1900). 

Nabl,  Monatshefte  f.  Chem.,  22,  737,  (1901) 

Sodium  tetrathionate  was  prepared  in  the  same  way  as  in  the  above  article.  If 
the  alkali  is  not  neutralized,  the  oxidation  of  the  thiosulphate  is  only  25%  complete 
and  there  is  also  formed  dithionate  and  sulphate  as  well  as  tetrathionate. 

Willstatter,  Ber.,  35,  1831,  (1903). 

He  states  that  the  action  of  hydrogen  peroxide  on  a  solution  of  sodium  thiosulphate 
is 

2Na2S2O3  4-  4H2O2  =  Na2S3O6  +  Na2SO4  +  4H2O 

This  is  in  disagreement  with  the  results  of  Nabl  (loc.  cit.} 
Thatcher,  Zeitschr.  f.  phys.  Chem.,  47,  641,  (1904). 

Sodium  tetrathionate  was  prepared  by  the  electrolytic  oxidation  of  sodium  thio- 
sulphate in  neutral  solution,  using  platinized  electrodes  with  a  definite  anode  potential 
difference.  He  considered  the  reaction  to  be  a  secondary  rather  than  a  primary  one, 
probably  brought  about  by  the  oxygen  which  is  formed  during  the  electrolysis  together 
with  the  aid  of  the  platinized  electrodes. 

Primary:      2S*O3 "  +  2F  =  S4O6" 

Secondary:  O"4-  2F  =  1/2  O2 

y20,  4-2S2(Y'=  S406"+0" 
Abel,  Monatshefte  f.   Chem.,  28,   1239,   (1907). 

Sodium   tetrathionate   was   prepared   in   two   ways. 

(a)  By  the  action  of  hydrogen  peroxide  on  sodium  thiosulphate  in  acetic  acid 
solution. 

H20,  +  2Na2S,03  -f  2CH3COOH  =  Na2S4O6  4-  2CH3COONa  4-  2H2O 

(b)  By  the  action  of  hypoiodite  on  thiosulphate  in  acetic  acid  solution. 

10'  -f  28,03"+  2H'  =  S406"-f  H20  +  I' 


Fromm,  Ber.,  40,  3397,  (1908). 

The  sodium  tetrathionate  was  prepared  by  the  method  of  Klobukow  (loc.  cit.}. 
He  analyzed  the  salt  by  determining  the  barium  sulphate;  also  by  determining  the  so- 
dium sulphate.  The  water  of  crystallization  was  determined  by  drying  the  salt  at 
110°  C. 

Stiasny  and  Das,  Jour.  Soc.  Chem.  Ind.,  31,  753,  (1912). 

Sodium  tetrathionate  was  prepared  by  the  action  of  potassium  dichromate  and 
sulphuric  acid  on  a  solution  of  sodium  thiosulphate.  They  give  three  possible  re- 
actions, but  in  only  one  is  the  tetrathionate  formed.  The  extent  to  which  each  of  these 
reactions  takes  place  depends  on  the  dilution  and  the  amounts  of  acid  and  thiosulphate 
present. 

Vanino  and  Schinner,  Ber.,  46,  1776,  (1914). 

Sodium  tetrathionate  was  prepared  by  the  method  of  Fordos  and  Gelis  (loc.  cit,}. 

About  50  grams  of  pure  sodium  thiosulphate  (Na2S2Os .  5H2O)  and  25  grams  of 
iodine  were  finely  pulverized  in  a  mortar,  placed  in  a  500  cc.  flask  and  treated  with  50 
cc.  of  absolute  alcohol.  The  pasty  mass  (at  the  ordinary  temperature)  was  kept  in 
constant  motion  by  means  of  a  shaking  machine  until  complete  decolorization,  requir- 
ing about  two  days.  Pulverized  iodine  was  now  added  until  permanent  coloration, 
and  then  100  cc.  of  absolute  alcohol.  The  separated  salt  was  washed  with  a  mixture  of 
absolute  alcohol  and  ether  until  the  wash  liquid  after  the  addition  of  some  water  and 
ammonia  no  longer  became  turbid  on  the  addition  of  silver  nitrate.  After  that  the  salt 
was  dried  in  the  air  between  filter  paper,  then  placed  in  a  beaker  and  dissolved  in  50  cc. 
to  60  cc.  of  distilled  water.  A  small  amount  of  iodine  dissolved  in  alcohol  was  added 
to  this  solution  until  there  was  a  permanent  coloration  of  iodine,  then  350  cc.  of  a  mix- 
ture of  absolute  alcohol  and  ether.  After  standing  some  time  the  salt  was  filtered  off, 
washed  with  absolute  alcohol-ether,  and  lastly  with  ether  only.  In  a  short  time  it 
lost  the  odor  of  ether  and  was  then  placed  in  a  stoppered  bottle. 

Sander,  Zeitschr.  angew.  Chem.,  28,  273,  (1915). 

The  tetrathionates  of  sodium  and  potassium  were  prepared  by  the  method  of  Fordos 
and  Gelis  (loc.  cit.}. 

26  grams  of  iodine  were  dissolved  in  alcohol  and  into  this  cooled  solution  a  satur- 
ated solution  of  50  grams  of  sodium  thiosulphate  (Na2S2Os .  SH^O)  or  39.5  grams  of  potas- 
sium thiosulphate  (at  room  temperature)  were  added  'gradually  by  means  of  a  drop 
funnel.  The  decomposition  of  the  thiosulphate  occurs  immediately  with  the  excess  of 
iodine,  and  the  tetrathionate  which  is  formed  being  insoluble  in  alcohol  separates  in 
small  crystals.  These  crystals  were  filtered  off  and  washed  with  alcohol  until  the  wash 
liquid  was  free  of  iodine  and  iodide,  then  dissolved  in  the  least  possible  amount  of  water 
and  reprecipitated  by  the  addition  of  alcohol.  The  crystals  were  filtered  off,  pressed 
between  filter  paper  and  finally  dried  over  sulphuric  acid. 

On  analysis  the  potassium  salt  was  found  to  be  pure  and  the  sodium  salt  to  be 
impure.  The  methods  of  analysis  used  were: 

1.  By  calcination  and  obtaining  the  sulphate. 


9 

2.  By  oxidation  with  mercuric  chloride  and  titrating  with  standard  NaOH. 

3.  By  oxidation  with  bromine  water  and  precipitating  as  barium  sulphate. 

4.  By  reduction  with  nascent  hydrogen  and  determining  the  amount  of  hydrogen 
sulphide. 

Related  Articles 

Plessy,  Ann.  chim.  phys.,  (3)  20,  162,  (1847). 

He  claimed  to  have  discovered  a  new  series  of  sulphur  acids  by  the  action  of  sul- 
phur monochloride  on  sulphurous  acid.  Salts  were  prepared  from  the  acids  by  neutral- 
ization with  carbonates. 

Fordos  and  Gelis,  Ann.  chim.  phys.,  (3)  22,  66,  (1848). 

They  were  unable  to  verify  the  results  of  Plessy  (loc.  cit.}. 

Mendeleeff,   Ber.,  3,  870,  (1870). 

Prin.  0}  Chem.  II,  284,   (1905). 

He  gives  the  persulphidic  structure  to  the  tetrathionates.  Debus,  Jour.  Chem. 
Soc.,  53,  351,  (1888)  states  that  Mendeleeff  adopted  the  structure  of  Blomstrand  (Chem. 
d.  Jetzzeit,  158). 

Persulphidic  Structure 
H-O-SO2 
S 

s 

H-O-SO2 
Gutman,  Ber.,  37,  1728,  (1905). 

He  prepared  sodium  tetrathionate  by  the  method  of  Fordos  and  Gelis  (loc.  cit.} 
and  Klobukow  (loc.  cit.}.     He  suggested  the  peroxidic  structure  for  tetrathionates. 
Peroxidic  Structure 

Na-0-S° 

0S 

O 
Na-O-Sg 

Gutman,  Ber.,  39,3614,  (1907). 

He  investigated  the  validity  of  the  results  obtained  by  Fordos  and  Gelis  (loc.  cit.} 
and  Kessler  (loc.  cit.}  on  the  action  of  sodium  hydroxide  on  sodium  tetrathionate. 

Gutman,  Ber.,  40,  300,  (1908). 

An  investigation  of  the  action  of  carbonates  of  sodium,  potassium  and  lithium  on 
sodium  tetrathionate. 

Debus,    Jour.  Chem.  Soc.,  53,  278,  (1888). 

Ann.  Chem.,  244,  76,  (1888). 

He  prepared  a  mixture  of  potassium  thionates  by  passing  sulphur  dioxide  through 
a  potassium  thiosulphate  solution. 


10 

9SO2  =  K2S506  +  K2S4O6  +  4K2S3O6 
Wackenroder's  solution  was  also  prepared,  the  acidity  determined,  and  an  equiva- 
lent amount  of  potassium  acetate  added  (assuming  pentathionic  acid).  The  solution 
was  evaporated  at  the  ordinary  temperature  and  potassium  pentathionate  obtained. 
He  further  states  "The  use  of  potassium  acetate  instead  of  potassium  hydroxide  is 
advantageous  because  all  the  acid  of  Wackenroder's  solution  can  be  converted  into  the 
potassium  salt,  and  the  hydric  acetate  which  is  set  free  tends  to  prevent  the  decompo- 
sition of  the  potassium  pentathionate.  The  mother  liquors  contain  much  potassium 
pentathionate  and  tetrathionate." 

The  salt  obtained  above  was  analyzed  by 

(a)  Oxidation  with  nitric  acid  and  precipitation  with  barium  chloride. 

(b)  Oxidation  with  bromine  water  and  precipitation  with  barium  chloride. 
The  results  of  the  analysis  gave  results  close  to  the  generally  accepted  ratios  of 

potassium  to  sulphur,  2:5. 

On  page  356  a  probable  structure  for  tetrathionates  is  given. 
K-S-S02 
O 
S 
K-0-S02 

Chancel  and  Diacon,   Compt.   rend.,   1,  710,    (1863). 

Jour.  f.  prak.  Chem.,  90,  55,  (1863). 

The  tetrathionates  of  copper  and  lead  were  prepared.  Tetrathionic  acid  was 
also  prepared  by  adding  sulphuric  acid  little  at  a  time  to  a  mixture  of  lead  thiosulphate 
and  lead  peroxide. 

2PbS2O3  +  PbO2  +  2SO3  =  PbS4O6  +  2PbSO4 
Vortmann,  Ber.,  22,.  2311,    (1889). 

Arsenic  is  completely  precipitated  by  sufficient  excess  of  thiosulphate;  in  presence 
of  arsenious  acid  there  is  obtained  in  the  filtrate  principally  tetrathionic  acid  besides 
a  trace  of  pentathionic  acid.  Sulphuric  acid  is  not  formed  or  only  in  traces.  If  too 
little  sodium  thiosulphate  is  present,  a  part  of  the  arsenious  acid  remains  in  solution, 
and  the  reaction  proceeds  according  to  the  equation: 

As2O3  +  9H2S2O3  =  As2S3  -f  3H2S4O6  +  3SO2  +  6H2O 

Two  thirds  of  the  sulphur  present  should  go  over  into  the  tetrathionate.  Two 
experiments  gave  16.08%  and  15.46%;  sulphur  instead  of  17.14%,  calculated  from  the 
sodium  thiosulphate. 

Marshall,  Jour.  Soc.  Chem.  Ind.,  16,  396,  (1897). 

The  tetrathionates  of  potassium  and  ammonium  were  prepared  by  the  action  of 

persulphates  on  thiosulphates. 

KaSoOs  +  2K2S203  =  K2S406  +  2K2SO4 
(NH4)2S208  +  2BaS203  =  (NH4)2S4O«  +  2BaSO4 


Mackenzie  and  Marshall,  Jour.  Chem.  Soc.,  II,  93,  1726,  (1908). 


11 

Potassium  tetrathionate  was  prepared  by  the  action  of  potassium  persulphate  and 
barium  thiosulphate. 

=  K2S4O6  +  2BaSO4 


PREPARATION 

Sodium  tetrathionate  was  first  prepared  by  following  the  method  given 
by  Biltz  and  Biltz  (Ubungbeispeile  aus  der  unorgan.  Experimentalchemie, 
122):  "50  grams  of  sodium  thiosulphate,  26  grams  of  iodine  and  5  grams 
of  water  are  pulverized  in  a  mortar  to  a  complete  homogeneous  light  brown- 
ish yellow  paste.  In  a  short  time  the  paste  is  washed  into  an  Erlenmeyer 
flask  using  alcohol  as  the  wash  liquid.  After  about  three  hours  the  pre- 
cipitated sodium  tetrathionate  is  filtered  off  using  suction  and  washed 
with  alcohol  until  the  filtered  alcohol  is  free  of  iodine.  The  crude  product 
is  dissolved  in  20  grams  to  25  grams  of  lukewarm  water,  filtered,  and 
alcohol  added  about  10  grams  at  a  time  until  about  50  grams  have  been 
added.  After  about  ten  hours,  during  which  time  the  mixture  has  been 
kept  away  from  the  air  either  in  an  Erlenmeyer  flask  or  a  vacuum  desic- 
cator, it  is  filtered  using  suction  and  the  crystals  washed  with  alcohol, 
and  dried  in  a  sulphuric  acid  desiccator.  The  crystals  are  colorless  and 
in  aggregates.  Yield  about  20  grams." 

The  above  method  is  that  of  Klobukow  (loc.  cit.}  somewhat  modified; 
practically  the  same  as  given  in  Biltz,  Hall  and  Blanchard  (Laboratory 
Methods  of  Inorganic  Chemistry,  1  32)  ;  and  somewhat  similar  to  that  given 
in  Rose-Finkener  (Handb.  der  analyt.  Chem.,  6  Aufl.,  II,  629). 

In  following  the  above  directions  it  was  found  that  the  yields  were  low 
and  variable,  being  from  20%  to  40%  of  the  theoretical. 

In  order  to  determine  if  the  yield  of  the  sodium  tetrathionate  could  be 
increased,  a  series  of  experiments  were  made  by  precipitating  the  salt  from 
alcoholic,  alcohol-ether,  and  water  solutions  and  allowing  them  to  stand 
over  night,  or  to  cool  them  for  two  or  three  hours  with  a  mixture  of  salt 
and  ice. 

I—  METHOD  OF  KLOBUKOW  (MODIFIED) 

The  conditions  under  which  the  results  in  Table  I,  A,  B,  and  C  were 
obtained  are  as  follows:  — 

.">()  grams  of  C.  P.  Na2S2O3.5H2O  were  finely  pulverized  in  a  mortar, 
5  cc.  of  alcohol  added  and  then  26  grams  of  resublimed  iodine,  which 
had  been  previously  finely  pulverized,  were  added  a  little  at  a  time  and 


12 

thoroughly  mixed  after  each  addition.  (Whenever  the  term  alcohol  is 
used  in  this  paper,  unless  otherwise  specified,  is  meant  alcohol  containing 
93%  alcohol  by  weight  or  about  95%  alcohol  by  volume).  The  contents 
of  the  mortar  were  transferred  to  a  beaker  using  alcohol  as  the  wash  liquid 
to  completely  remove  all  the  residue  and  then  allowed  to  stand  from  two 
to  three  hours.  It  was  then  filtered  through  a  Biichner  and  washed  free 
of  iodine  and  iodide  by  means  of  alcohol  and  then  sucked  dry ;  redissolved 
in  warm  water,  filtered  and  reprecipitated  as  specified  in  A,  B,  and  C  of 
Table  I. 

II— METHOD  OF  SANDER  (See  D  of  Table  I) 

Sodium  tetrathionate  was  prepared  according  to  Sander  (loc.  cit.)  except 
that  absolute  alcohol-ether  (1:1),  by  volume,  at  room  temperature  was 
used  instead  of  cooled  absolute  alcohol.  The  precipitated  sodium  tetra- 
thionate was  redissolved  in  the  smallest  amount  of  warm  water,  filtered, 
and  added  to  a  mixture  of  absolute  alcohol-ether  (1:1)  and  allowed  to 
stand  over  night. 

TABLE  I. 
A.     Precipitation  by  allowing  to  stand  over  night. 

Cc.  of  water  used          Temperature 

to  dissolve  the  of  water  Precipitated  Cc.  Yield 

sodium  tetrathionate  °C.  from  used  in  % 

25  20  alcohol  60  20 

18  50  alcohol  60  50 

18  45  alcohol  60  35 
17  50  absolute  alcohol  100  65 

17  50  absolute 

alcohol-ether  100  65 

B.  Precipitation  by  cooling  with  a  mixture  of  salt  and  ice  to  — 10° 

for  three  hours. 

19  45  alcohol  60  65 
14                           55             absolute  alcohol                     60  65 
16                           50             absolute  alcohol                     75  70 
14                            55                            absolute 

alcohol-ether          =150  70 

C.  Precipitation  by  cooling  the  saturated  water  solution  to  — 5°  for 

three  hours. 

18  50  water  18  40 

D.  Precipitation  according  to  Sander. 
14  50  absolute 

alcohol-ether         =       500  60 


13 

By  reducing  the  volume  of  water  in  which  the  sodium  tetrathionate  is 
redissolved  before  precipitation,  and  warming  it  to  increase  the  solubility 
and  using  absolute  alcohol  or  absolute  alcohol-ether  (1:1)  instead  of  alco- 
hol, the  yield  was  practically  doubled.  It  was  found  that  a  fair  yield  may 
be  obtained  from  a  water  solution  by  cooling  with  a  freezing  mixture  of 
salt  and  ice. 

Somewhat  better  yields  were  obtained  by  cooling  the  solutions  rather 
than  by  allowing  them  to  stand  over  night,  unless  they  were  placed  out 
of  doors  when  the  weather  was  cold,  and  under  such  conditions  the  yield 
would  sometimes  run  as  high  as  80%. 

ANALYSIS  FOR  SULPHUR 

In  order  to  get  an  idea  of  the  purity  of  the  sodium  tetrathionate  which 
had  been  precipitated  from  a  concentrated  water  solution  by  the  addition 
of  absolute  alcohol,  a  number  of  experiments  were  run  the  results  of  which 
are  shown  in  Table  II,  A,  B,  and  C  and  in  which  the  sulphur  found  was 
compared  with  the  theoretical  amount  of  sulphur,  assuming  the  sodium 
tetrathionate  to  be  Na2S4O6. 2H2O. 

Procedure: — 0.100  gm.  to  0.150  gm.  of  sodium  tetrathionate  which  had 
been  precipitated  from  alcohol  solution  and  thoroughly  dried  between 
filter  papers  were  dissolved  in  water  and  bromine  water  added  to  distinct 
bromine  coloration. 

Na2S4O6  +  14Br  +  10H2O  =  Na2SO4  +  3H2SO4  +  14HBr 

The  solution  was  then  boiled  until  the  bromine  had  been  driven  off 
and  precipitated  with  barium  chloride. 

The  conditions  under  which  the  sulphate  ions  were  precipitated  in  this 
series  of  experiments  and  all  others  which  follow  were :  two  or  three  drops 
of  concentrated  hydrochloric  acid  were  added  to  the  solution,  then  heated 
to  boiling  and  barium  chloride  solution  (made  by  dissolving  25  gm.  of 
BaCl2.2H2O  in  one  liter  of  water)  added  slowly  with  constant  stirring 
until  about  one  and  one-half  times  the  theoretical  amount  had  been  added. 
The  solution  was  allowed  to  stand  for  one-half  hour  and  then  filtered 
through  an  ashless  filter. 

The  concentration  of  the  sulphate  ion  before  precipitation  was  kept  so 
that  the  adsorption  by  the  barium  sulphate  after  precipitation  was  prac- 
tically equal  to  its  solubility,  viz.,  about  one  gram  of  barium  sulphate  from 
a  liter  of  solution. 

The  Results: — The  results  of  this  series  of  experiments  are  recorded  in 


14 

Table  II.  In  trials  1  to  5  inclusive,  the  sodium  tetrathionate  solution 
was  contained  in  a  beaker  and  the  bromine  water  was  dropped  into  it 
from  a  pipette,  stirring  constantly. 

In  trials  6  to  9  inclusive,  the  sodium  tetrathionate  solution  was  con- 
tained in  a  closed  Erlenmeyer  flask  and  the  bromine  water  was  added  from 
a  drop  funnel.  In  trial  10  the  tip  of  the  pipette  was  placed  below  the 
surface  of  the  sodium  tetrathionate  solution  contained  in  a  beaker  when 
the  bromine  was  added,  stirring  constantly. 

TABLE  II 

A.     The  sodium  tetrathionate  solution  contained  in  a  beaker  and  the 
bromine  water  dropped  in  from  a  pipette. 


Sodium  tetra- 
thionate 
used 
Gm. 

BaSO4  calc. 
from  sodium 
tetrathion- 
ate taken. 
Gm. 

Sulphur  calc. 
from  sodium 
tetrathionate       BaSO* 
taken               found 
Gm.                  Gm. 

Sulphur 
found 
Gm. 

Error 

BaS04 
Gm. 

Error 
in 
Sulphur 
Gm. 

1. 

0. 

1X)15 

0.3094 

0.0425 

0 

.3049 

0.0419 

-0 

0045 

-0 

.0006 

2. 

0. 

1016 

0.3097 

0.0426 

0 

.2999 

0.0412 

-0 

.0098 

-0 

.0014 

3. 

0. 

1503 

0.4582 

0.0629 

0 

.4526 

0.0622 

-0 

.0056 

—  0 

.0007 

4. 

0. 

1508 

0.4597 

0.0632 

0 

.4533 

0.0623 

-0 

.0064 

-0 

.0009 

5. 

0. 

1515 

0.4618 

0.0634 

0 

.4569 

0.0628 

-0 

.0049 

-0 

.0006 

B.  The  sodium  tetrathionate  solution  contained  in  a  closed  flask  and  the 

bromine  water  added  from  a  drop  funnel. 

6.  0.1522        0.4639        0.0637        0.4580        0.0629         -0.0059         -0.0008 

7.  0.1514        0.4615        0.0634        0.4619        0.0634         +0.0004  0.0000 

8.  0.1508        0.4597        0.0632        0.4576        0.0629         -0.0021         -0.0003 

9.  0.1506        0.4591         0.0631         0.4573        0.0628         -0.0018         -0.0003 

C.  The  sodium  tetrathionate  solution  contained  in  a  beaker  and  the 
bromine  water  added  from  a  pipette  with  the  tip  below  the  surface 

of  the  solution. 
10.      0.1510        0.4603        0.0633        0.4584        0.0630         -0.0019         -0.0003 

The  results  of  Table  II  show  that  the  sodium  tetrathionate  precipitated 
by  the  addition  of  absolute  alec  hoi  is  quite  pure.  Also,  in  the  oxidation 
of  the  solution  of  sodium  tetrathionate,  certain  precautions  must  be  ob- 
served in  order  to  prevent  loss  of  sulphur. 

QUALITATIVE  TESTS 

Samples  of  sodium  tetrathionate  precipitated  from  alcohol,  alcohol- 
ether,  and  water  solutions  were  dissolved  in  water  and  tested  qualitatively, 
about  10  cc.  of  the  solution  being  used  for  each  test. 


15 

Solutions  added.  Results 

Barium  chloride  In  somewhat  concentrated  solutions  a  slight  cloudiness 

was  produced. 

Lead  acetate  None. 

Iodine  Small  part  of  a  drop  gave  coloration.     N/10  used. 

Mercurous  nitrate  Yellow  precipitate. 
Dilute  potassium 

permanganate  Red  color.     No  brown  precipitate. 

Ferric  chloride  Slight  coloration  in  somewhat  concentrated  solutions. 

In  dilute  solutions  the  salts  dissolved  clear,  while  in  more  concentrated 
solutions  there  was  a  slight  cloudiness.  All  sodium  tetrathionate  solu- 
tions were  neutral  to  litmus. 

For  tables  showing  the  characteristic  tests  for  sulphur  salts  see 

Lieb,  Ann.,  207,  90,   (1881). 

Zeitschr.  phys.  Chem.,  47,  652,  (1904). 

Prescott  and  Johnson  Qual.,  Chem.  Anal.,  7th  Ed.,  326. 

In  the  above  tests  the  following  would  be  indicated: — Barium  chloride 
in  presence  of  hydrochloric  acid  would  detect  presence  of  sulphates. 

Lead  acetate  would  detect  presence  of  iodides. 

Iodine  would  detect  the  presence  of  sulphites  and  thiosulphates. 

Mercurous  nitrate:  dithionates  no  precipitate;  sulphites,  thiosulphates, 
and  trithionates  a  black  precipitate;  tetrathionates  and  pentathionates 
a  yellow  precipitate. 

Dilute  potassium  permanganate;  dithionates  and  trithionates  a  red 
precipitate;  tetrathionates  and  pentathionates  bleach. 

The  qualitative  tests  show  possible  traces  of  free  sulphur,  and  some 
thiosulphate,  the  salt  crystallized  from  water  solution  showing  the  least. 

Pozzi-Escot,  Bui.  soc.  Mm.,  (4),  13,  401,  (1913)  gives  a  very  delicate 
test  for  thiosulphates,  sulphites  and  polythionates  not  giving  the  reaction. 

Take  2  cc.  of  solution  containing  the  thiosulphate  and  add  2  cc.  of  a 
ten  per  cent  ammonium  molybdate  solution ;  then  add  5  cc.  of  concentrated 
sulphuric  acid.  A  blue  ring  will  form  between  the  layers,  which  may  be 
more  readily  seen  by  using  a  white  background.  He  states  .00005  gm. 
of  sodium  thiosulphate  may  be  detected. 

In  order  to  test  the  above  .0020  gm.  of  sodium  thiosulphate  was  dis- 
solved in  500  cc.  of  water  and  2  cc.  of  the  solution  tested.  It  gave  a  blue 
ring  between  the  layers  after  about  three  minutes,  using  a  white  back- 
ground. 


16 
COMPARATIVE  ANALYSES  FOR  PURITY 

A  comparison  of  the  purity  of  the  various  samples  of  .spdium  tetrathio- 
nate  was  made  by  determining  the  amount  of  sodium  sulphate,  •shown  in 
Table  III,  A,  B,  C,  and  D;  and  also  by  determining  the  total  sulphur  as 
barium  sulphate,  shown  in  Table  IV,  A,  B,  C,  and  D. 

In  determining  the  sodium  sulphate  it  was  assumed  that  the  sodium 
tetrathionate  had  the  composition  Na2S4O6.2H2O,  and  when  heated  de- 
composed into  sodium  sulphate,  sulphur  dioxide  and  water. 

The  results  in  Table  III  were  obtained  by  weighing  out  about  one  gram 
of  the  sodium  tetrathionate  in  a  crucible  and  heating  at  first  with  a  very 
low  Bunsen  flame  for  a  half  hour  or  more  keeping  the  lid  on  the  crucible 
and  gradually  raising  the  heat  until  the  full  heat  of  the  Bunsen.  Then 
it  was  heated  with  the  partial  heat  of  a  blast  lamp  for  five  minutes,  placed 
in  the  desiccator,  cooled  and  weighed. 

TABLE  III 

A.  Sodium  tetrathionate  prepared  by  method  of  Klobukow,  modified,  dis- 

solved in  water  and  precipitated  by  addition  of  absolute  alcohol. 

Sodium  tetrathionate  Na2SO4 

used.  calc.  Na2SO4  Error  in  Na2SO4. 

Gm.  Gm.  Found.  Gm. 

1.0482  0.4862  0.4883  +0.0021 

1.0055  0.4664  0.4682  +0.0018 
1.0069                            0.4670                        0.4694  +0.0024 
1.0007                            0.4641                        0.4668  +0.0027 
1.0017                            0.4646                        0.4667  +0.0021 
0.7083                            0.3285                        0.3306  +0.0021 
0.7362                             0.3414                         0.3435  +.00021 

B.  Sodium  tetrathionate  prepared  by  method  of  Klobukow  modified,  dis- 
solved in  water  and  precipitated  by  the  addition  of  absolute  alcohol- 
ether  (1:1). 

1.0081  0.4676  0.4716  +0.0040 

1.0063  0.4667  0.4700  +0.0033 

C.  Sodium  tetrathionate  prepared  by  the  method  of  Sander  dissolved  in 
water  and  precipitated  by  the  addition  of  absolute  alcohol-ether  (1:1). 

1.0056  0.4664  0.4760  +0.0096 
1.0094                           0.4682                        0.4778  +0.0096 

D.  Sodium  tetrathionate  prepared  by  method  of  Klobukow  modified,  dis- 
solved in  water  and  precipitated  from  the  water  solution  by  cooling  with 

a  mixture  of  salt  and  ice. 

1.0038  0.4656  0.4646  -0.0010 

1.0069  0.4670  0.4661  —0.0009 


17 

The  results  given  in  Table  IV  were  obtained  by  using  the  samples  of 
sodium  tetrathionate  as  used  to  obtain  the  results  in  Table  III,  and  in 
the  calculations  the  same  assumption  was  made  as  to  the  composition 
of  the  sodium  tetrathionate,  viz.,  Na2S4O6.2H2O. 

About  .1500  gm.  of  the  sodium  tetrathionate  were  weighed,  dissolved 
in  water,  and  bromine  water  added  from  a  .pipette,  the  tip  of  which  was 
below  the  surface  of  the  solution  while  the  bromine  water  was  added, 
stirring  constantly  until  there  was  a  distinct  coloration  due  to  the  bromine 
and  then  the  excess  of  bromine  boiled  off. 

The  same  precautions  were  observed  in  the  precipitation  of  the  barium 
sulphate  as  in  Table  II. 

TABLE  IV 

A.  Sodium  tetrathionate  prepared  by  the  method  of  Klobukow  modified, 
dissolved  in  water  and  precipitated  by  the  addition  of  absolute  alcohol. 

Sodium  tetra-       BaSO4  Sulphur  BaSO4  Sulphur  Error  Error  in 

thionate  used.         calc.  calc.  found.  found.  in  BaSO4  sulphur. 

Gm.  Gm.  Gm.  Gm.  Gm.  Gm.  Gm. 

0.1529        0.4661         0.0640        0.4646        0.0638         -0.0015         -0.0002 
0.1668        0.5085        0.0699        0.5065        0.0696         -0.0020         -0.0003 

B.  Sodium  tetrathionate  prepared  by  the  method  of  Klobukow  modified, 
dissolved  in  water,  and  precipitated  by  the  addition  of  absolute  alcohol- 
ether  (1:1). 

0.1547        0.4716        0.0648        0.4672        0.0642         -0.0044         -0.0006 
0.1560        0.4756        0.0653        0.4715        0.0648         -0.0041         -0.0005 

C.  Sodium  tetrathionate  prepared  by  the  method  of  Sander,  dissolved  in 
water  and  precipitated  by  the  addition  of  absolute  alcohol-ether  (1:1). 

0.1519        0.4631         0.0636        0.4573        0.0628         -0.0058         -0.0008 
0.1510        0.4603        0.0632        0.4544        0.0624         -0.0059         -0.0008 

D.  Sodium  tetrathionate  prepared  by  method  of  Klobukow  modified,  and 
precipitated  from  the  water  solution  by  cooling  with  a  mixture  of  salt 

and  ice. 

0.1785        0.5441         0.0748        0.5436        0.0747         -0.0005         -0.0001 
0.1515        0.4618        0.0635        0.4611         0.0634         -0.0007         -0.0001 

The  results  of  the  analyses  of  the  various  samples  of  sodium  tetrathionate 
in  Tables  III  and  IV  show  that  the  salt  crystallized  from  the  water  solution 
has  the  highest  degree  of  purity.  However,  it  might  be  added  that  the 
salt  crystallized  from  the  water  solution  would  give  a  positive  test  for  the 
presence  of  thiosulphates  by  using  the  ammonium  molybdate  sulphuric 
acid  test  suggested  by  Pozzi-Escot  (loc.  cit.)  if  considerable  amount  of  the 


18 

sodium  tetrathionate  be  used.  The  samples  of  sodium  tetrathionate 
prepared  by  the  method  of  Klobukow  modified,  dissolved  in  water  and 
precipitated  by  the  addition  of  absolute  alcohol  or  absolute  alcohol-ether 
(1:1),  or  prepared  by  the  method  of  Sander  and  precipitated  by  the  addi- 
tion of  absolute  alcohol-ether,  always  gave  a  decided  test  for  thiosulphates 
when  the  ammonium  molybdate  sulphuric  acid  test  was  applied. 

DETERMINATION  OF  WATER  OF  CRYSTALLIZATION 

Fordos  and  Gelis  (loc.  cit.)  determined  the  water  of  crystallization  in 
sodium  tetrathionate  by  difference.  Fromm  (loc.  cit.)  found  it  by  drying 
the  sodium  tetrathionate  in  the  air  at  110°. 

The  water  of  crystallization  was  determined  in  the  present  investi- 
gation by  means  of  a  small  gas  combustion  furnace  in  an  atmosphere  of 
carbon  dioxide,  the  arrangement  being  shown  in  Fig.  1 .  The  carbon 
dioxide  was  obtained  from  a  Kipp  generator  not  shown  and  passed  through 
a  sodium  carbonate  solution  A,  and  then  through  two  calcium  chloride 
drying  columns  B.  The  bottle  C  and  stopcock  D  were  used  for  conven- 
ience. The  asbestos  shield  K  protected  the  absorption  tube  L  from  the 
heat  of  the  furnace.  Ordinary  copper  oxide  wire  I  was  used,  and  the  copper 
spiral  H  was  reduced  in  the  usual  way  by  means  of  methyl  alcohol.  The 
reduced  copper  spiral  H  takes  up  the  free  sulphur  formed  from  the  de- 
composition of  the  sodium  tetrathionate  and  decomposes  any  hydrogen 
sulphide  which  may  form.  During  any  one  combustion  only  a  small 
part  of  the  reduced  copper  spiral  H  next  to  the  boat  G  was  attacked  or 
used  by  the  sulphur.  A  very  small  amount  of  the  copper  oxide  wire  was 
reduced,  showing  that  a  very  little  hydrogen  sulphide  was  formed. 

The  temperature  at  which  the  combustions  were  carried  out  was  the 
full  heat  of  the  gas  combustion  furnace  in  which  the  glass  tube  was  a  bright 
cherry  red. 

Before  making  a  determination,  the  furnace  was  ignited  and  the  train 
swept  out  with  carbon  dioxide  passing  at  the  rate  of  two  bubbles  per  second 
until  the  weight  of  the  calcium  chloride  absorption  tube  L  was  constant 
to  within  .4  mg.  The  time  required  for  this  was  from  three  to  five  hours. 

The  time  required  for  a  determination  after  placing  the  sodium  tetra- 
thionate in  the  combustion  tube  was  from  three  to  four  hours,  which  in- 
cluded the  gradual  heating  up  of  the  furnace,  the  combustion  and  the 
sweeping  out  of  the  train. 


19 


20 

The  calcium  chloride  absorption  tube  L,  after  each  combustion  was 
closed  on  each  side  and  placed  in  a  large  sulphuric  acid  desiccator  for 
one-half  hour  before  each  weighing. 

Preliminary  to  the  determination  of  the  water  of  crystallization  in  the 
sodium  tetrathionate,  two  combustions  were  made  with  some  selected 
crystals  of  C.  P.  sodium  thiosulphate,  the  results  being  shown  in  Table 
V,  A.  The  sodium  tetrathionate  used  in  the  experiments  shown  in  Table 
V,  B,  was  crystallized  from  a  water  solution  by  cooling  with  salt  and  ice 
and  dried  between  filter  papers. 

TABLE  V 

A.  Determination  of  water  of  crystallization  in  hydrous  sodium  thiosulphate. 

Weight  of  sodium        Weight  of  sodium          Weight  of  water       Weight  of  water 
thiosulphate  taken,     tetrathionate  taken.  found.  calc.  Error  in 

Gm.  Gm.  Gm.  Gm.  Gm. 

0.3841  0.1391  0.1394  -0.0003 

0.4852  0.1753  0.1761  —0.0008 

B.  Determination  of  water  of  crystallization  in  hydrous  sodium 

tetrathionate. 

1.1998  0.1414  0.1411  +0.0003 

1.1914  0.1407  0.1401  +0.0006 

In  making  the  calculations  for  the  water  of  crystallization  in  hydrous 
sodium  thiosulphate  and  hydrous  sodium  tetrathionate  in  A  and  B  of 
Table  V,  their  compositions  were  assumed  to  be  Na2S2O3.5H2O  and  Na2- 
S4O6.2H2O  respectively. 

The  results  in  B  of  Table  V  show  that  each  molecule  of  hydrous  sodium 
tetrathionate  contains  two  molecules  of  water  of  crystallization. 

BEHAVIOR  WHEN  EXPOSED  TO  AIR  AT  ORDINARY  ATMOSPHERIC  PRES- 
SURES; TO  AIR  OVER  SULPHURIC  ACID  AT  ORDINARY  AND  REDUCED 
ATMOSPHERIC  PRESSURES 

Klobukow  (loc.  oil.),  Biltz  and  Biltz  (loc.  cit.)  and  Sander  (loc.  cit.)  in 
the  preparation  of  sodium  tetrathionate  direct  to  dry  the  salt  over  sul- 
phuric acid.  Sander  (loc.  cit.}  stated  that  he  was  unable  to  prepare  pure 
hydrous  sodium  tetrathionate,  yet  he  prepared  pure  anhydrous  potassium 
tetrathionate  using  the  same  method,  drying  both  salts  over  sulphuric 
acid. 

In  order  to  determine  the  behavior  of  hydrous  sodium  tetrathionate 
when  exposed  to  the  air  at  ordinary  atmospheric  pressure,  to  air  over 


21 

sulphuric  acid  at  ordinary  and  also  reduced  atmospheric  pressures,  the 
experiments  the  results  of  which  are  shown  in  Table  VI,  A,  B,  and  C 
were  made.  The  sodium  tetrathionate  was  spread  out  on  one  of  two 
tared  watch  glasses. 

TABLE  VI 

A.  Hydrous  sodium  tetrathionate  exposed  to  air. 

Weight  of  sodium  Loss  in  weight  of 

tetrathionate  Time  exposed.  sodium  tetrathionate. 

Gm.  Days.  Gm.. 

1.0040  0  0.0000 

1.0045  2  +0.0005 

1.0044  10  +0.0004 

B.  Hydrous  sodium  tetrathionate  exposed  to  air  over  concentrated 

sulphuric  acid  at  ordinary  atmospheric  pressure. 

1.0042  0  0.0000 

1.0035  1  0.0007 

1.0032  2  0.0010 

1.0016  4  0.0026 

1.0011  5  0.0031 

1.0010  6  0.0032 

0.9998  8  0.0044 

0.9982  11  0.0060 

C.  Hydrous  sodium  tetrathionate  exposed  to  air  over  concentrated 
sulphuric  acid  at  reduced  atmospheric  pressure  (from  two  to  five 

cm.  of  Hg). 

0.9982  0  0.0000 

0.9970  2  0.0012 

0.9960  3  0.0022 

0.9789  15  0.0193 

0.9647  27  0.0335 

The  results  obtained  in  Table  VI,  A,  show  that  the  weight  of  hydrous 
sodium  tetrathionate  is  fairly  constant  in  the  air,  the  slight  changes  shown 
being  due  to  decided  changes  in  the  humidity;  those  in  B  and  C  show  a 
gradual  loss  in  weight  over  sulphuric  acid,  either  at  ordinary  or  reduced 
atmospheric  pressure.  Further,  the  results  show  that  the  dissociation 
pressure  of  hydrous  sodium  tetrathionate  is  of  such  magnitude  that  it 
should  not  be  dried  over  concentrated  sulphuric  acid  for  any  considerable 
length  of  time. 

SUGGESTED  METHOD  FOR  PREPARATION 

Weigh  out  50  grams  of  Na2S2O3.5H2O  and  26  grams  of  iodine  and  pul- 


verize  each  in  separate  mortars.  To  the  finely  pulverized  sodium  thio- 
sulphate  in  the  mortar,  add  approximately  5  cc.  of  distilled  water  and 
25  cc.  of  alcohol  and  thoroughly  mix.  Then  add  the  iodine  a  little  at  a 
time,  thoroughly  mixing  after  each  addition,  until  all  has  been  added  and 
there  remains  a  slight  excess  of  iodine.  Add  25  cc.  of  alcohol  and  allow 
to  stand  from  twenty  minutes  to  one  half  hour,  filter  through  a  Biichner 
using  suction,  and  wash  free  of  iodine  and  iodide  by  means  of  alcohol. 

The  absence  of  iodine  may  be  told  by  the  color  of  the  wash  alcohol, 
and  the  absence  of  iodide  by  the  addition  of  a  few  drops  of  a  dilute  solution 
of  lead  acetate  to  the  wash  alcohol.  Lead  acetate  when  added  to  the  wash 
alcohol  forms  a  yellow  precipitate  of  lead  iodide  when  an  iodide  is  present, 
and  a  white  precipitate  of  lead  tetrathionate  when  it  is  absent. 

The  precipitate  after  it  has  been  sufficiently  washed  with  alcohol  is 
sucked  nearly  dry  on  the  Biichner  in  order  to  remove  most  of  the  alcohol, 
dissolved  in  the  smallest  possible  amount  of  water  (15  cc.  to  17  cc.),  warmed 
to  50°  to  60°  and  filtered  through  a  Gooch  using  suction  into  a  test  tube 
which  is  placed  within  a  one  liter  Erlenmeyer  filter  flask.  To  this  filtrate 
add  ten  to  fifteen  drops,  or  if  necessary  more,  of  iodine  in  alcohol  solution. 
There  should  be  a  slight  iodine  coloration. 

The  sodium  tetrathionate  may  be  precipitated  or  crystallized  from 
the  filtrate  by  the  addition  of  absolute  alcohol-ether  (1:1)  or  absolute 
alcohol  and  allowing  to  stand  over  night,  or  by  cooling  with  a  mixture  of 
salt  and  ice. 

(I)  Precipitation  by  ike  addition  of  absolute  alcohol-ether  or  absolute  alcohol 

and  allowing  to  stand  over  night. 

Add  the  filtrate  to  a  crystallizing  dish  and  then  add  100  cc.  of  absolute 
alcohol-ether  (1:1)  and  place  in  an  empty  desiccator  (best  a  vacuum 
desiccator)  for  at  least  twelve  hours. 

Instead  of  using  absolute  alcohol-ether  (1:1),  100  cc.  of  absolute  alcohol 
may  be  used  with  nearly  the  same  yield. 

(II)  Precipitation  by  the  addition  of  absolute  alcohol-ether  or  absolute  alcohol 

and  cooling  by  means  of  salt  and  ice. 

Add  the  filtrate  to  a  small  beaker  and  then  add  100  cc.  of  absolute  alcohol- 
ether  (1  :  1)  and  cool  by  placing  in  a  mixture  of  salt  and  ice  for  two  or  three 
hours,  keeping  the  beaker  covered.  Absolute  alcohol  may  be  substituted 
for  the  absolute  alcohol-ether  as  in  (I). 

Whether  the  sodium  tetrathionate  is  precipitated  by   (I)   or  (II),   it 


23 

should  be  filtered  using  suction  and  sucked  as  dry  as  possible,  then  placed 
between  filters  and  dried.  It  should  then  be  crystallized  from  a  water 
solution  by  cooling  as  this  removes  practically  all  the  thiosulphate. 

Recrystallization  from  Water.  The  dry  sodium  tetrathionate  obtained 
from  the  absolute  alcohol-ether  or  the  absolute  alcohol  mixtures  is  dis- 
solved in  the  smallest  amount  of  water  at  50°  to  60°  in  a  beaker  and 
cooled  by  a  mixture  of  salt  and  ice  for  two  or  three  hours.  This  will  give 
about  one  half  of  the  sodium  tetrathionate  dissolved.  The  sodium  tetra- 
thionate precipitated  should  be  filtered  off  using  suction  to  remove  the 
greater  part  of  the  water,  then  placed  between  filter  papers  until  dry. 
After  the  salt  has  been  dried,  it  should  be  placed  in  a  glass  stoppered 
bottle. 

In  case  it  is  desired,  the  greater  part  of  the  sodium  tetrathionate  still 
dissolved  in  the  mother  liquor  or  filtrate  may  be  precipitated  by  the  addi- 
tion of  absolute  alcohol-ether  (1:1)  or  absolute  alcohol. 

Stability  of  Sodium  Tetrathionate.  Two  different  samples  of  sodium 
tetrathionate  crystallized  from  water  and  thoroughly  dried  between  filter 
paper  were  kept  in  glass  stoppered  bottles  for  one  and  one-half  years. 
One  sample  had  a  very  slight  tinge  of  yellow  and  when  dissolved  in  water 
showed  some  turbidity;  the  other  sample  remained  perfectly  white  and 
when  dissolved  in  water  showed  only  the  slightest  trace,  of  turbidity. 

Sander  (loc.  cit.)  says  that  solutions  of  pure  tetrathionates  may  be  boiled 
without  decomposition.  He  further  states  that  the  presence  of  sodium 
thiosulphate  greatly  accelerates  the  decomposition. 

BARIUM  TETRATHIONATE 

BIBLIOGRAPHY 

Fordos  and  Gelis,  Ann.  chim.  phys.,  (3)  6,  489(1842). 
Jour.f.  prak.  Chem.,  28,  476(1843). 

Barium  tetrathionate  was  prepared  by  the  action  of  iodine  on  barium  thiosulphate. 

Barium  thiosulphate  was  mixed  with  water  forming  a  thin  paste  and  small  amounts 
of  iodine  were  added  until  it  just  began  to  color;  the  excess  of  iodine  and  iodide  were 
washed  out  with  alcohol.  The  white  powder  was  dissolved  in  the  smallest  amount  of 
water  possible,  filtered  and  allowed  to  evaporate.  The  crystals  were  more  readily 
obtained  when  absolute  alcohol  was  added  to  the  solution. 

The  barium  tetrathionate  had  a  bitter  taste,  was  very  soluble  in  water,  slightly  in 
alcohol,  kept  at  the  ordinary  temperature  in  dry  air  but  became  yellow  in  a  short  time 
in  moist  air. 


24 

They  made  an  analysis  of  the  salt  as  follows: — A  known  amount  of  the  salt  was 
dissolved  in  water  and  oxidized  with  chlorine.  The  solution  was  filtered,  and  the 
barium  sulphate  formed  was  weighed.  The  sulphuric  acid  formed  during  the  oxidation 
was  precipitated  with  barium  chloride. 

The  water  of  crystallization  was  found  by  difference. 

Wackenroder,  Archiv.  der  Pharm.,  47,  272,  (1846). 

Wackenroder's  solution  was  prepared  by  passing  hydrogen  sulphide  into  a  satur- 
ated water  solution  of  sulphur  dioxide  at  room  temperature  until  there  was  an  excess 
of  hydrogen  sulphide.  The  solution  was  then  shaken  with  some  oxidized  copper  turn- 
ings and  filtered.  This  filtrate  was  immediately  completely  neutralized  with  barium 
carbonate  and  a  little  barium  hydroxide,  and  after  a  few  hours  the  solution  was  ready 
to  be  used. 

(a)  A  known  weight  of  the  barium  pentathionate  solution  was  taken  and  the  barium 
determined  by  precipitation  with  sulphuric  acid. 

(&)  A  known  weight  of  the  barium  pentathionate  solution  was  taken  and  a  solution 
of  potassium  hydroxide  added  and  the  solution  evaporated  to  dryness.  The  residue 
was  dissolved  in  water,  nitric  acid  added,  and  the  solution  boiled.  This  solution  was 
evaporated  to  dryness,  the  residue  dissolved  in  water  and  a  solution  of  barium  chloride 
added.  The  results  of  the  first  trial  showed  the  ratio  of  the  barium  to  the  sulphur  to 
be  1 : 5.23.  In  the  second  trial  the  ratio  of  barium  to  sulphur  was  found  to  be  1 : 5. 

Wackenroder,  Archiv.  of  Pharm.,  48,  140,  (1846). 

This  was  a  continuation  of  the  previous  article  and  the  results  are  no  more  satis- 
factory. The  water  of  crystallization  was  determined  by  heating  the  barium  salt  to 
105°  C. 

Lenoir,  Ann.  Chem.  u.  Pharm.,  62,  253,  (1847). 

Barium  pentathionate  was  prepared  by  treating  Wackenroder's  solution  with  barium 
carbonate,  the  salt  being  precipitated  by  the  addition  of  alcohol.  On  analysis  the  salt 
was  found  to  have  practically  the  composition,  BaSsOe^HaO. 

The  water  of  crystallization  was  determined  by  combustion  with  lead  chromate; 
at  the  same  time  carbon  dioxide  was  determined  and  the  carbon  corresponded  to  2.93% 
alcohol  which  was  present  in  the  salt. 

Ludwig,  Archil),  der  Pharm.,  51,  259,  (1847). 

Potassium  tetrathionate  was  prepared  from  Wackenroder's  solution  by  half  neu- 
tralizing with  potassium  carbonate.  Barium  and  lead  salts  were  prepared  in  a  similar 
way. 

Kessler,  Jour.f.  prak.  Chem.,  47,  35,  (1849). 

Pogg.  Ann.  Phys.  Chem.,  74,  255,  (1849). 

Barium  tetrathionate  was  prepared  by  using  equivalent  amounts  of  solutions  barium 
acetate  and  tetrathionic  acid  and  then  adding  alcohol.  The  crystals  were  tabular. 
The  analysis  of  the  salt  was  not  given. 


25 

Sobrero  and  Selmi,  Ann.  chim.  phys.,  (3)  28,  210,  (1850). 

Barium  tetrathionate  was  prepared  from  Wackenroder's  solution  by  the  addition 
of  barium  carbonate.  On  analysis  the  results  obtained  for  baryte,  sulphur,  oxygen 
combined  with  sulphur  and  water  agree  very  favorably  with  those  of  Fordos  and  Gelis 

(loc.  cit.}. 

Spring,  Ann.  Chem.  Pharm.,  199,  97,  (1879). 

The  potassium  and  barium  teirathionates  were  prepared  from  Wackenroder's 
solution  by  neutralizing  with  the  carbonates  and  then  adding  alcohol.  The  salts  showed 
on  analysis,  K:S  =  2:4  and  Ba:S  =  1:4. 

Pfeiffer,  Arch.  Pharm.,  14,  334,  (1879). 

Potassium  tetrathionate  was  prepared  from  Wackenroder's  solution  which  had 
been  brought  to  a  specific  gravity  of  1.30  by  evaporation  on  a  water  bath.  This  acid 
was  dissolved  in  a  mixture  of  ether-amyl  alcohol  and  absolute  alcohol  and  a  dilute 
solution  of  potassium  carbonate  added.  The  barium  salt  was  prepared  in  a  similar 
way  except  it  was  precipitated  from  alcohol. 

The  salts  were  analyzed  in  two  ways. 

(a)  By  oxidation  with  bromine  in  hydrochloric  acid  solution  and  precipitation 
with  barium  chloride. 

(b)  By  heating  and  determining  the  sulphates. 

He  concluded  from  his  results  that  pentathionic  acid  does  not  exist  free  nor  in  the 
form  of  salts. 

Smith  and  Takamatsu,  Jour.  Chem.  Soc.  37,  592,  (1880). 

Barium  tetrathionate  was  prepared  from  Wackenroder's  solution  by  neutralizing 
with  barium  carbonate  and  precipitating  with  alcohol.  The  salt  on  analysis  proved 
to  be  BaSiOe.l  H2O.  They  further  state,  "We  have  proved  to  our  own  satisfaction 
that  the  attempt  to  neutralize  pentathionic  acid  with  alkaline  earth  carbonates  simply 
results  in  the  formation  of  tetrathionates  with  the  separation  of  sulphur." 

Lewes,  Jour.  Chem.  Soc.  39,  68,  (1881). 

The  pentathionates  and  tetrathionates  of  potassium  and  barium  were  prepared. 

Wackenroder's  solution  was  concentrated  to  the  separation  of  sulphur  and  filtered. 
The  acidity  was  then  determined  by  titration  with  standard  potassium  hydroxide, 
then  a  weak  solution  of  barium  hydroxide  sufficient  to  half  neutralize  the  acid  was  added ; 
the  next  day  it  was  filtered  to  remove  the  sulphur  and  barium  sulphate  which  formed. 
The  filtrate  was  then  placed  over  sulphuric  acid  in  a  vacuum  and  left  to  crystallize. 
After  standing  a  few  days  some  sulphur  separated  and  the  solution  was  again  refiltered 
and  replaced  in  the  vacuum  over  sulphuric  acid.  At  the  end  of  eighteen  days  it  de- 
posited a  crop  of  fine  needle  shaped  crystals  together  with  a  small  quantity  of  sulphur. 
Three  crops  of  crystals  were  obtained,  and  each  crop  was  then  dissolved  in  a  small  amount 
of  water  and  recrystallized  a  second  time.  The  first  crop  showed  on  analysis  to  be 
BaS4O6.3H2O;  the  second  seemed  to  be  a  mixture  of  the  pentathionate  and  the  tetra- 
thionate; the  third  seemed  to  have  the  composition 


26 

The  methods  he  used  in  the  analysis  were, 

(a)  Oxidation  with  nitric  acid,  removal  of  all  traces  of  acid,  filtering  and  weighing 
the  barium  sulphate.  The  rest  of  the  sulphur  being  oxidized  to  sulphuric  acid  was 
precipitated  as  barium  sulphate. 

(&)  Oxidation  with  chlorine  in  potassium  hydroxide  solution. 

(c}  Boiling  the  solution  with  mercuric  cyanide  and  estimation  of  sulphuric  acid, 
mercuric  sulphide  and  free  sulphur,  according  to  the  equation  of  Kessler,  (loc.  cit.}. 

(d)  Evaporation  of  solution  to  dryness  with  potassium  hydroxide  and  fuse  with 
potassium  hydroxide  and  potassium  nitrate,  precipitating  as  barium  sulphate. 

The  water  of  crystallization  was  determined  by  combustion  with  lead  chromate. 

Spring,  Ann.  Chem.,  213,  329,  (1882). 

The  potassium  and  barium  salts  were  prepared  from  Wackenroder's  solution  by 
neutralizing  with  carbonates  and  precipitating  with  alcohol.  He  also  treated  potas- 
sium thiosulphate  with  sulphur  monochloride  and  obtained  a  salt  which  showed  on 
analysis  K:S  2:4.02. 

He  has  compiled  a  list  of  the  results  of  the  different  investigators  who  have  pre- 
pared potassium  pentathionate  from  Wackenroder's  solution.  The  ratio  of  potassium 
to  sulphur  varies  from  2:3.305  to  2:5.23,  the  average  being  2:4.506. 

Spring  held  that  what  is  called  pentathionic  acid  is  nothing  but  sulphur  dissolved 
in  tetrathionic  acid. 
Smith  and  Takamatsu,  Jour.  Chem.  Soc.,  41,  162,  (1882). 

Potassium  and  barium  salts  were  prepared  in  a  similar  way  to  that  already  used 
in  their  previous  article  (loc.  cit.}. 

Curtius  and  Henkel,  Jour.  j.  prak.  Chem.,  N.  F.  37,  142,  (1888). 

Barium  tetrathionate  was  prepared  from  Wackenroder's  solution  and  barium 
carbonate. 

The  Wackenroder's  solution  was  filtered  and  placed  in  a  large  flask  and  barium 
carbonate  added  a  little  at  a  time  until  an  excess  had  been  added.  It  was  kept  in  the 
flask  for  several  hours  during  which  time  it  was  thoroughly  shaken;  the  solution  was 
then  filtered,  the  filtrate  being  clear  and  did  not  react  with  litmus.  A  portion  of  the 
filtrate  was  analyzed  and  the  ratio  of  Ba  to  S  was  found  to  be  1:4. 

The  salt  was  obtained  by  filtering  any  excess  barium  carbonate  and  adding  alcohol. 
The  barium  tetrathionate  thus  obtained  was  dissolved  in  a  small  amount  of  water  and 
reprecipitated  by  alcohol.  The  salt  obtained  from  the  second  precipitation  was  an- 
alyzed and  found  to  have  the  composition  BaS4Oe.2H2O. 

The  Analysis: — a  known  amount  of  the  salt  was  dissolved  in  water  and  then  oxi- 
dized with  chlorine  in  potassium  hydroxide  solution.  The  solution  was  then  filtered 
and  the  barium  sulphate  weighed.  The  sulphuric  acid  formed  during  the  oxidation 
was  precipitated  by  the  addition  of  barium  chloride  and  weighed  as  barium  sulphate. 

The  water  of  crystallization  was  determined  by  combustion  with  lead  chromate. 

Hertlein,  Zeitschr.  f.  phys.  Chem.,  19,  287,  (1896). 

Potassium  Tetrathionate: — To  a  completely  saturated  solution  of  potassium  thio- 


27 

sulphate  at  room  temperature,  so  arranged  as  to  be  cooled  and  constantly  stirred,  was 
a  water  solution  of  iodine  in  potassium  iodide  added  dropwise,  and  after  each  addition 
of  iodine  waited  until  it  had  been  decolorized.  The  crystallized  potassium  tetrathionate 
was  filtered  off  from  time  to  time  to  avoid  the  action  of  iodine  on  the  tetrathionate. 

Barium  Tetrathionate: — It  was  prepared  by  making  a  paste  with  barium  thio- 
sulphate  and  water  and  adding  solid  iodine  in  small  amounts  at  a  time  until  a  distinct 
brown  color  remained.  The  salt  was  then  washed  with  strong  alcohol  and  the  excess 
of  iodine  and  iodide  removed,  dissolved  in  water  and  a  small  amount  of  alcohol  added 
which  precipitated  a  small  amount  of  barium  tetrathionate  and  which  was  of  particular 
aid  in  removing  the  finely  divided  sulphur  and  barium  sulphate.  The  solution  was 
then  filtered  and  the  rest  of  the  barium  tetrathionate  precipitated  by  the  further  addi- 
tion of  alcohol. 

The  concentrated  solutions  of  the  barium  salt  decompose  slightly  and  on  this  ac- 
count it  was  impossible  to  get  it  perfectly  clear.  The  salt  dissolves  with  residue  but 
the  solutions  are  always  more  or  less  opalescent;  solutions  of  moderate  concentration 
do  not  show  this. 

PREPARATION 

I.  Previous  Methods  Used. 

Barium  tetrathionate  was  first  prepared  by  Fordos  and  Gelis  (loc.  cit.). 
Since  that  time  many  investigators  have  prepared  the  salt,  their  methods 
being  as  follows: — 

(1)  By  action  of  iodine  on  barium  thiosulphate.     Fordos  and  Gelis 
(loc.  cit.)',  Hertlein  (loc.  cit). 

(2)  From  Wackenroder's  solution. 

(a)  By    half    neutralizing    with    potassium    carbonate.     Ludwig 
(loc.  cit.}. 

(b)  By  half  neutralizing  with  barium  hydroxide.     Lewes  (loc.  cit.). 

(c)  By  complete  neutralization  with  barium  carbonate.     Sobrero 
and  Selmi  (loc.  cit.) ;  Spring  (loc.  cit.) ;  Pfeiffer  (loc.  cit.) ;  Smith  and  Taka- 
matsu  (loc.  cit.)',  Curtius  and  Henkel  (loc.  cit.). 

(3)  By  action  of  barium  acetate  on  tetrathionic  acid.     Kessler  (loc. 
cit.). 

II.  General  Procedure  of  Method  Used. 

25  grams  of  BaSgOa.lH^O  and  12.5  grams  of  resublimed  iodine  were 
finely  pulverized  in  separate  mortars.  Then  from  80  to  100  cc.  of  alcohol 
of  definite  density  were  added  to  the  mortar  containing  the  barium  thio- 
sulphate and  the  iodine  added  a  little  at  a  time  thoroughly  mixing  after 
each  addition,  until  all  the  iodine  had  been  added  and  there  remained  a 
slight  excess  of  iodine. 


28 

The  mixture  was  left  in  the  mortar  from  two  to  three  hours  stirring 
occasionally,  transferred  to  a  Biichner  using  alcohol  as  the  wash  liquid 
and  washed  free  of  iodine  and  iodide  by  means  of  alcohol. 

The  residue  was  dissolved  in  the  smallest  possible  amount  of  water  at 
a  temperature  not  above  20°,  filtered  through  a  specially  prepared  Gooch 
and  the  barium  tetrathionate  precipitated  from  the  filtrate  by  the  addition 
of  alcohol,  absolute  alcohol,  absolute  alcohol-ether  (1:1),  or  acetone  either 
by  allowing  to  stand  over  night  or  by  cooling,  the  results  being  shown  in 
A,  C,  and  D  of  Table  VII.  In  B  of  Table  VII  is  shown  the  result  obtained 
by  cooling  the  water  solution  of  barium  tetrathionate. 

III.  Preparation  of  Barium  Thiosulphate. 

The  barium  thiosulphate  was  prepared  by  mixing  solutions  containing 
equivalent  amounts  of  sodium  thiosulphate  and  barium  chloride. 

463.9  grams  of  C.  P.  hydrous  sodium  thiosulphate  were  dissolved  in  550 
cc.  of  water,  and  456.6  grams  of  C.  P.  hydrous  barium  chloride  were  dis- 
solved in  1500  cc.  of  water,  both  solutions  being  filtered  before  used. 

The  solution  of  sodium  thiosulphate  was  heated  nearly  to  boiling  and 
kept  hot  while  the  barium  chloride  solution  was  added  from  a  burette 
at  the  rate  of  two  or  three  drops  per  second,  stirring  constantly. 

After  all  the  barium  chloride  had  been  added,  the  barium  thiosulphate 
was  washed  by  decantation  six  or  eight  times,  then  placed  on  a  Buchner 
and  washed,  using  suction  until  free  of  chlorides. 

IV.  Difficulties  Encountered. 

In  the  first  experiments  in  which  barium  tetrathionate  was  prepared 
several  difficulties  were  encountered  and  the  yields  were  very  low. 

(1)  Barium  thiosulphate  does  not  form  paste. 

The  barium  thiosulphate  did  not  form  a  paste  with  water  as  did  the 
sodium  thiosulphate  and  for  this  reason  the  condition  for  complete  re- 
action was  not  so  good. 

(2)  Reaction  incomplete. 

When  alcohol  alone  was  added  to  the  barium  thiosulphate  and  the  iodine 
added  a  little  at  a  time,  the  reaction  would  not  go  to  completion  and  a 
large  residue  of  barium  thiosulphate  remained.  These  results  are  shown 
in  Table  VII,  trials  1  to  8  inclusive.  This  difficulty  was  probably  of  a 
mechanical  nature  due  to  a  protective  coating  of  barium  tetrathionate 
formed  around  the  particles  of  barium  thiosulphate  thus  preventing  the 
contact  with  the  iodine  in  solution.  When  water  was  added  to  the  alcohol 


29 

which  was  added  to  the  barium  thiosulphate  before  the  addition  of  the 
iodine,  the  reaction  would  go  to  completion.  The  addition  of  water  to 
the  alcohol  either  increased  the  solubility  of  the  barium  tetrathionate 
and  thus  removed  the  protective  coating,  or  permitted  the  barium  tetra- 
thionate to  be  formed  in  a  more  granular  form  and  the  protective  coating 
did  not  form;  in  either  case  the  reaction  would  go  to  completion. 

(3)  Determination  of  density  of  alcohol  used. 

Since  it  was  shown  that  water  must  be  added  to  the  alcohol  which 
was  added  to  the  barium  thiosulphate  before  the  addition  of  iodine,  it 
was  necessary  to  determine  the  density  of  alcohol  used  which  would  permit 
the  reaction  to  go  to  completion  and  still  not  have  the  water  content  high 
enough  to  dissolve  any  considerable  amounts  of  barium  tetrathionate. 
This  was  done  by  increasing  the  density  of  the  alcohol  used  until  there 
was  no  residue  of  barium  thiosulphate. 

(4)  The  condition  of  the  barium  tetrathionate  formed. 

The  barium  tetrathionate,  obtained  when  undiluted  alcohol  was  added 
to  the  barium  thiosulphate  before  the  addition  of  iodine,  was  gummy  and 
difficult  to  filter;  while  the  barium  tetrathionate,  obtained  when  diluted 
alcohol  was  used,  was  crystalline  and  easily  filtered. 

TABLE  VII 

A.     Precipitated  by  allowing  to  stand  over  night.     Alcohol  specific  gravity 
0.817  at  20°,  added  to  the  barium  thiosulphate. 


Cc.  of  water 
Cc.  of  alcohol      used  to  dis- 
added  to  barium   solve  barium 
Trial,      thiosulphate        tetrathionate. 

1                      350                        14 

Precipitated 
from. 

alcohol     = 

Cc. 

used. 

60 

Yield 
in  %. 
8 

2 

3  cc.  water  20  cc. 

14 

ab.  alcohol    = 

60 

21.5 

alcohol 

3 

20 

35 

ab.  alcohol    = 

100 

12.1 

4 

40 

26 

ab.  alcohol     = 

100 

10.7 

5 

35 

20 

ab.  alcohol     = 

200 

13.7 

6 

50 

20 

ab.  ale.  -ether     = 

200 

26.9 

7 

50 

20 

acetone      = 

170 

10.2 

Precipitated  by  cooling  a  water  solution.     Alcohol  specific  gravity  0.817 
at  20°  added  to  the  barium  thiosulphate. 

8  50  23  water        =       23  9.1 

Precipitated  from  an  absolute  alcohol-ether  solution  (1:1)  by  cooling. 
Alcohol  specific  gravity  0.887  at  20°  added  to  barium  thiosulphate. 

9  85  25  abs.  alc.-ether     =     200  40.3 


30 


D.     Precipitated  by  allowing  to  stand  over  night.     Alcohol  specific  gravity 
0.887  at  20°  added  to  barium  thiosulphate. 

10  90  35  abs.  alc.-ether     =     250  59. 

11  90  36  abs.  alc.-ether     =     400  70. 

12  110  27  abs.  alc.-ether     =     400  65. 

13  100  30  abs.  alc.-ether     =     500  70 . 

% 
The  results  of  the  above  experiments  show  that  the  highest  yields  were 

obtained  when  absolute  alcohol-ether  was  added  to  the  nitrate  and  allowed 
to  stand  over  night.  The  low  results  in  the  first  eight  trials  was  largely 
due  to  the  fact  that  the  reaction  between  the  iodine  and  barium  thiosul- 
phate did  not  go  to  completion. 

COMPARATIVE  ANALYSIS  FOR  PURITY 

I.     By  Heating  the  Barium  Tetrathionate. 

In  order  to  get  an  idea  of  the  purity  of  the  barium  tetrathionate  a  series 
of  experiments  were  made,  the  results  of  which  are  shown  in  Tables  VIII 
and  IX. 

TABLE  VIII 

A.     Barium  tetrathionate  prepared  by  the  method  of  Fordos  and  Gelis 
modified,  dissolved  in  water  and  precipitated     by  the  addition  of 
absolute  alcohol-ether  (1:1). 


Trial. 

1 

2 

3 

4 

5 

6 

7 

8 

9 
10 
11 
12 
13 
14 


Barium  tetia- 

Barium  sulphate 

Barium  sulphate 

Error  in 

thionate  used. 

calculated. 

found. 

barium  sulphate. 

Gm. 

Gm. 

Gm. 

Gm. 

0.5025 

0.2950 

0.2968 

+0.0018 

0.5048 

0.2963 

0.2979 

+0.0016 

0.5002 

0.2936 

0.2948 

+0.0013 

0.5031 

0.2953 

0.2981 

+0.0028 

0.4955 

0.2908 

0.2887 

-0.0021 

0.5060 

0.2970 

0  .  2954 

-0.0016 

0.5047 

0.2952 

0.2943 

-0.0019 

0.5020 

0.2947 

0.2923 

-0.0024 

0.5099 

0.2993 

0  .  2994 

+0.0001 

0.4983 

0.2925 

0  .  2927 

+0.0002 

0.5180 

0.3041 

0.3055 

+0.0014 

0.5046 

0.2962 

0.3008 

+0.0046 

0  .  5023 

0.2949 

0.2974 

+0.0025 

0.5007 

0.2939 

0.2961 

+0.0022 

B. 


15 
16 


Barium  tetrathionate  prepared  by  the  method  of  Fordos  and  Gelis 

modified,  dissolved  in  water  and  cooled. 

0.5139  0.3017  0.3014  -0.0003 

0.5014  0.2943  0.2942  -0.0001 


31 

In  Table  VIII  are  shown  results  obtained  by  heating  the  barium  tetra- 
thionate. 

About  one  half  gram  of  the  hydrous  barium  tetrathionate  was  weighed  out 
into  a  crucible  and  heated  with  a  very  low  Bunsen  flame  for  about  one- 
half  hour,  keeping  the  lid  loosely  fitted  on  the  crucible,  then  gradually 
raising  the  temperature  to  the  full  heat  of  the  Bunsen  for  ten  minutes, 
placed  in  a  desiccator,  cooled  and  weighed.  In  some  cases  a  few  drops 
of  concentrated  sulphuric  acid  were  added  to  the  barium  sulphate  and 
then  carefully  driven  off  by  heating;  this  made  no  change  in  the  results. 

In  calculating  the  barium  sulphate  from  the  hydrous  barium  tetrathio- 
nate, the  composition  of  the  hydrous  barium  tetrathionate  was  assumed  to 
be  BaS4O6.2H2O,  and  the  products  formed  when  heated  to  be  barium 
sulphate,  sulphur  dioxide  and  sulphur. 

II.     By  Oxidation  of  Barium  Tetrathionate  and  Precipitating  with  Barium 

Chloride  Solution 

The  results  shown  in  Table  IX  were  obtained  by  weighing  out  given 
amounts  of  hydrous  barium  tetrathionate,  dissolving  in  water,  oxidizing 
with  bromine  water  and  afterwards  boiling  off  the  excess,  and  precipitating 
the  sulphate  ion  by  the  addition  of  a  barium  chloride  solution  observing 
all  the  precautions  given  under  Table  II. 

The  hydrous  barium  tetrathionate  was  obtained  by  addition  of  an  abso- 
lute alcohol -ether  (1:1)  solution  to  a  freshly  filtered  concentrated  water 
solution  of  barium  tetrathionate  and  allowing  to  stand  over  night. 

TABLE  IX 

Barium  tetrathionate  Barium  sulphate  Barium  sulphate  Error  in  barium 

taken.  calculated.  found.  sulphate. 

Gm.  Cm.  Gm.  Gm. 

1.0000  2.3480          2.2976          -0.0514 

0.5000  1.1740          1.1604          -0.0136 

0.5000  1.1740          1.1587          -0.0153 

The  results  shown  in  Table  VIII,  trials  1  to  4  inclusive  were  obtained 
from  two  different  samples,  but  the  samples  were  analyzed  about  three 
weeks  after  they  were  prepared;  the  results  in  trials  5  to  8  inclusive  were 
obtained  from  two  other  different  samples  analyzed  two  days  after  their 
preparation ;  the  results  in  trials  9  to  14  were  from  three  entirely  different 
samples  analyzed  two  days  after  their  preparation. 

The  results  in  B,  Table  VIII,  were  obtained  from  a  sample  precipitated 


32 

from  a  water  solution,  carefully  dried  between  niters  and  immediately 
analyzed. 

It  might  also  be  stated  that  the  results  obtained  in  trials  9  to  14  inclu- 
sive were  from  samples  prepared  during  the  hot  summer  months. 

The  results  of  both  Tables  VIII  and  IX  show  the  hydrous  barium  tetra- 
thionate  to  be  quite  pure,  but  it  slowly  decomposes  particularly  above 
20°. 

WATER  OF  CRYSTALLIZATION 

Fordes  and  Gelis  (loc.  cit.)  obtained  the  salt  from  a  water  solution  and 
found  that  each  molecule  of  the  salt  contained  two  molecules  of  water  of 
crystallization,  the  result  being  obtained  by  difference.  Sobrero  and 
Selmi  (loc.  cit.)  obtained  results  in  agreement  with  those  of  Fordos  and 
Gelis.  Lewes  (loc.  cit.)  obtained  two  salts  of  hydrous  barium  tetrathionate, 
one  of  which  contained  one  and  the  other  three  molecules  of  water  of  crystal- 
lization. The  results  were  obtained  by  combustion  with  lead  chromate. 
Curtius  and  Henkel  (loc.  cit.)  determined  the  water  of  crystallization  by 
combustion  with  lead  chromate  and  found  it  to  contain  two  molecules 
of  water  of  crystallization.  Hertlein  (loc.  cit.)  prepared  barium  tetra- 
thionate according  to  the  method  of  Fordos  and  Gelis,  precipitated  by 
means  of  alcohol  and  dried  the  salt  over  sulphuric  acid  and  found  that  it 
contained  one  molecule  of  water  of  crystallization.  He  does  not  state 
the  results  of  his  analysis  nor  does  he  state  what  method  he  used. 

BEHAVIOR  OF  THE  HYDROUS  SALT  WHEN  EXPOSED  TO  AIR;  TO  AIR  OVER 
CONCENTRATED  SULPHURIC  ACID  AND  TO  AIR  SATURATED  WITH 

MOISTURE 

In  order  to  determine  the  behavior  of  hydrous  barium  tetrathionate 
when  exposed  to  air,  air  over  concentrated  sulphuric  acid,  and  air  saturated 
with  moisture,  a  series  of  experiments  were  carried  out,  the  results  of  which 
are  shown  in  Table  X. 

The  hydrous  barium  tetrathionate  was  spread  out  on  one  of  two  tared 
watch  glasses.  In  A,  the  watch  glasses  were  exposed  to  air;  in  B,  to  air 
over  concentrated  sulphuric  acid  in  a  desiccator;  in  C,  to  air  over  water 
in  a  desiccator. 

The  results  of  Table  X  seem  to  show  that  hydrous  barium  tetrathionate 
is  slightly  deliquescent  when  exposed  to  air.  Further,  that  when  exposed 


33 

to  air  over  concentrated  sulphuric  acid  it  slowly  loses  some  of  its  water 
of  crystallization. 

TABLE  X 

A.  Hydrous  barium  tetrathionate  exposed  to  air. 

Weight  of  hydrous 

barium  tetrathionate.  Time  exposed.  Loss  in  weight.  Gain  in  weight. 

Gm.  Days.  Gm.  Gm. 

1.0058  0  0.0000 

1.0058  2  0.0000 

1.0075  10  0.0017 

B.  Hydrous  barium  tetrathionate  exposed  to  air  over  concentrated 
sulphuric  acid. 

1.0075                               0  0.0000  

1.0040                              2  0.0035  

0.9977                              8  0.0098  

0.9927                            14  0.0148  

0.9918                            20  0.0157  

C.  Exposed  to  saturated  air. 

1.0052  0  0.0000 

1.2905  2  0.2853 

SUGGESTED  METHOD  FOR  PREPARATION 

Weigh  out  50  grams  of  BaS2Os.lH2O  and  25  grams  of  iodine,  placing 
each  in  separate  mortars  and  pulverize  them  very  fine.  To  the  barium 
thiosulphate  in  the  mortar  add  100  cc.  of  alcohol  specific  gravity  approxi- 
mately 0.887  at  20°  and  thoroughly  mix.  Then  add  the  iodine  a  little 
at  a  time,  mixing  thoroughly  after  each  addition,  until  all  the  iodine  has 
been  added  and  there  remains  a  slight  excess  of  iodine.  The  addition  and 
mixing  should  require  about  three  quarters  of  an  hour.  Allow  the  mixture 
to  remain  in  the  mortar  a  short  time  after  all  the  iodine  has  been  added 
and  filter  through  a  Buchner  using  suction. 

Wash  the  precipitate  free  of  iodine  and  iodide  by  use  of  alcohol.  The 
absence  of  iodine  may  be  told  by  the  color  of  the  wash  alcohol ;  the  absence 
of  iodide  by  the  addition  of  a  few  drops  of  a  dilute  solution  of  lead  acetate. 

After  these  impurities  have  been  removed,  the  precipitate  is  dried  as 
much  as  possible  by  pressing  between  filter  paper  to  remove  most  of  the 
alcohol.  This  nearly  dry  precipitate  is  then  dissolved  in  the  least  possible 
amount  of  water  (about  65  cc.)  at  not  above  20°.  This  solution  is  then 
filtered  using  suction  through  a  specially  prepared  Gooch,  which  consists 
of  two  separate  layers  of  barium  sulphate  and  flowers  of  sulphur  with  a 


34 

layer  of  asbestos  on  the  top  and  bottom  and  also  between  each  of  the 
four  layers.  This  solution  is  best  filtered  into  a  test  tube  placed  within 
an  Erlenmeyer  filtering  flask.  To  the  filtrate  add  several  drops  of  iodine 
dissolved  in  alcohol  to  a  slight  iodine  coloration.  This  filtrate,  which 
usually  has  a  slight  turbidity,  is  added  to  700  cc.  of  absolute  alcohol- 
ether  (1:1)  in  a  crystallizing  dish,  placed  in  an  empty  vacuum  desiccator 
and  the  air  removed  and  allowed  to  stand  from  twelve  to  twenty-four 
hours.  If  the  weather  is  cold  the  yield  is  increased  by  placing  out  of  doors. 
The  yield  is  60%  to  75%  of  the  theoretical. 

Recrystallization  from  a  water  solution. 

Hydrous  barium  tetrathionate  may  also  be  obtained  by  cooling  the 
water  solution  by  means  of  a  mixture  of  salt  and  ice.  The  rate  of  crystal- 
lization is  extremely  slow  and  the  yield  not  very  satisfactory. 

QUALITATIVE  DECOMPOSITION 

The  salts  of  the  tetrathionate  decompose  into  a  sulphate,  sulphur  dioxide, 
and  sulphur  when  heated.  In  order  to  get  an  idea  of  the  decomposition 
of  tetrathionates  in  a  boiling  solution,  a  series  of  qualitative  experiments 
were  made. 

About  1  gram  of  hydrous  barium  tetrathionate  was  dissolved  in  100  cc. 
of  water  and  transferred  to  an  Erlenmeyer  flask  which  was  attached  to 
a  Liebig  condenser.  The  solution  was  heated  and  became  decidedly 
turbid  as  soon  as  it  began  to  boil. 

The  odor  of  sulphur  dioxide  was  plainly  noticeable  at  the  mouth  of  the 
condenser,  and  when  the  evolved  gas  was  led  into  a  dilute  solution  of 
potassium  permanganate  it  was  readily  bleached. 

The  residue  consisted  of  barium  sulphate  and  sulphur  with  a  slight 
trace  of  sulphite  and  thiosulphate. 

The  solution  was  boiled  for  30  hours  and  when  tested  with  mercurous 
nitrate  solution  gave  a  yellow  precipitate  indicating  the  presence  of  tetra- 
thionate or  pentathionate  or  both,  or  possibly  higher  thionates,  but  the 
absence  of  any  appreciable  amounts  of  trithionate,  sulphite,  or  thiosul- 
phate. Further,  tests  were  made  to  determine  if  any  hydrogen  sulphide 
were  formed  during  the  decomposition. 

(I)  Filter  paper  moistened  with  lead  acetate  solution  was  held  at  the 
mouth  of  the  condenser  and  negative  results  obtained. 

(II)  Several  drops  of  lead  acetate  solution  were  added  to  the  solution 


35 

of  barium  tetrathionate  and  the  solution  boiled  with  a  reflux  for  one 
hour  before  any  darkening  was  noticeable.  At  the  end  of  two  hours  the 
solution  began  to  turn  black,  and  at  the  end  of  six  hours  it  was  black. 

The  results  of  the  above  qualitative  tests  show  that  the  barium  tetra- 
thionate solution  when  boiled  decomposes  into  barium  sulphate,  sulphur 
dioxide,  and  sulphur. 

QUANTITATIVE  DECOMPOSITION 

(I)     Preliminary. 

Before  making  the  quantitative  determinations  some  preliminary  experi- 
ments were  made  to  get  some  idea  of  the  time  required  for  the  decomposi- 
tion. 

1.  1  gram  of  hydrous  barium  tetrathionate  was  dissolved  in  water  and 
placed  in  a  flask  attached  to  a  reflux  condenser  and  boiled  8.5  hours. 
The  solution  was  filtered  and  again  boiled  2  hours.     The  weight  of  barium 
sulphate  obtained  by  the  second  boiling  was  .0143  grams. 

2.  1  gram  of  hydrous  barium  tetrathionate  was  treated  exactly   as   in 
1  except  it  was  boiled  the  first  time  for  8  hours.     The  solution  was  filtered 
and  again  boiled  for  5.5  hours.     The  weight  of  barium  sulphate  obtained 
by  the  second  boiling  was  .0179  grams. 

3.  1  gram  of  hydrous  barium  tetrathionate  was  treated  as  in  1  except 
it  was  boiled  for  7.5  hours.     The  weight  of  barium  sulphate  obtained  was 
.4160  grams  as  compared  to  .5870  grams,  the  theoretical  yield. 

(II)  Description  of  the  Apparatus. 

After  considerable  experimenting  the  set-up  shown  in  Fig.  2  was  chosen, 
although  in  carrying  out  the  experiments  two  absorption  tubes  in  series 
were  used. 

The  carbon  dioxide  was  generated  by  a  Kipp  not  shown  and  then  passed 
through  a  solution  of  sodium  carbonate  contained  in  A  to  the  decomposi- 
tion flask  C,  the  inlet  tube  extending  below  the  surface  of  the  solution. 
The  decomposition  flask  C  was  attached  to  a  reflux  condenser  B  in  order 
to  prevent  loss  by  boiling  and  thus  keep  the  volume  of  the  solution  constant. 
Connected  to  the  reflux  condenser  B  was  a  ten  bulbed  Meyer  absorption 
tube  D  which  contained  the  bromine  water  or  alkaline  hypobromite  to 
oxidize  the  evolved  sulphur  dioxide.  E  was  filled  with  some  of  the  same 
solution  as  was  used  in  the  absorption  tube. 


36 

The  type  of  absorption  tube  used  was  the  same  as  used  by  Lunge,  Jour. 
Soc.  Chem.  Ind.,  9,  1013  (1890). 

(Ill)     Procedure. 

The  apparatus  was  first  tested  to  be  sure  there  were  no  leaks.  After 
the  set-up  was  found  to  be  gas  tight,  1.0000  gram  of  hydrous  barium  tetra- 
thionate  was  dissolved  in  water  and  transferred  quantitatively  to  the 
decomposition  flask  C  so  there  were  100  cc.  of  solution  in  the  flask.  The 
air  in  the  system  was  then  driven  out  by  the  carbon  dioxide  and  the  solu- 


Fig.  2. — Decomposition  and  Absorption  Apparatus. 

tion  heated.  After  the  boiling  had  started  the  carbon  dioxide  was  con- 
tinued at  the  rate  of  about  two  bubbles  per  second  during  the  entire  time 
of  the  boiling.  When  the  boiling  was  discontinued,  the  system  was  swept 
out  by  carbon  dioxide  for  one  half  hour. 

The  analysis  shown  in  Table  XI  consists  of  three  parts. 

(1)  Determination  of  barium  sulphate  obtained  from  the  direct  de- 
composition of  the  barium  tetrathionate  during  the  boiling. 


37 

The  contents  of  the  decomposition  flask  was  transferred  quantitatively 
to  a  beaker,  together  with  the  small  amount  of  sulphur  which  collected 
in  the  lower  part  of  the  condenser.  The  solution  was  then  filtered  through 
a  hard  filter  and  the  filter  thoroughly  washed  with  water.  The  residue 
on  the  filter,  which  consisted  of  barium  sulphate  and  sulphur,  was  washed 
into  a  beaker  and  liquid  bromine  added,  the  solution  being  kept  warm 
for  three  hours.  The  decomposition  flask  was  also  treated  with  hot  bro- 
mine water  to  remove  any  adhering  particles  of  sulphur,  and  this  solution 
added  to  that  containing  the  barium  sulphate  and  sulphur. 

The  free  sulphur  was  oxidized  to  sulphuric  acid,  while  the  barium  sul- 
phate remained  unchanged. 

The  solution  was  then  boiled  to  remove  the  bromine  and  filtered  through 
a  weighed  Gooch,  the  increase  in  weight  being  the  barium  sulphate  formed 
from  the  direct  decomposition  of  the  barium  tetrathionate. 

(2)  Determination  of  barium  sulphate  obtained  from  the  sulphur  formed 
during  the  boiling. 

The  filtrate  obtained  from  (1)  should  contain  all  the  sulphur  formed 
during  the  decomposition  by  boiling  as  sulphuric  acid.  The  sulphate 
ion  was  precipitated  by  the  addition  of  a  solution  of  barium  chloride, 
the  barium  sulphate  being  that  obtained  from  the  oxidation  of  the  sulphur. 

(3)  Determination    of   barium    sulphate    obtained   from   the    sulphur 
dioxide  formed  during  the  boiling. 

When  bromine  was  used  in  the  absorption  tubes  as  in  trials  1  to  12 
inclusive,  the  contents  of  the  tubes  was  transferred  quantitatively  to  a 
beaker,  the  excess  bromine  boiled  off,  and  precipitated  by  the  addition 
of  a  solution  of  barium  chloride. 

When  alkaline  hypobromite  was  used  in  the  absorption  tubes  as  in 
trials  13,  14  and  15  the  contents  of  the  tubes  was  transferred  quantita- 
tively to  a  beaker,  made  slightly  acid  with  hydrochloric  acid  and  care- 
fully evaporated  to  dry  ness,  the  last  stages  being  on  a  water  bath.  The 
beaker  containing  the  residue  was  then  heated  in  an  air  oven  at  120° 
for  two  hours,  cooled,  and  the  residue  dissolved  in  water  and  the  solution 
filtered  to  remove  the  silica.  The  sulphate  ion  was  then  precipitated  by 
the  addition  of  a  solution  of  barium  chloride,  the  barium  sulphate  being 
that  obtained  from  the  oxidation  of  the  sulphur  dioxide. 
(IV)  Purification  of  Bromine. 

Since  practically  all  bromine  contains  small  amounts  of  sulphuric  acid 


38 

and  bromine -was  to  be  used  to  oxidize  the  sulphur  dioxide  evolved,  it  was 
necessary  to  remove  the  sulphate  from  the  bromine  before  using  it. 

500  grams  of  ordinary  N.  F.  bromine  was  washed  five  times  with  water 
in  a  separatory  funnel;  then  10  grams  of  barium  hydroxide  were  dissolved 
in  water  and  added  to  the  bromine  in  a  separatory  funnel  and  shaken  for 
two  hours;  the  bromine  was  then  washed  twice  with  water  and  poured 
into  a  long  necked  distilling  flask  containing  50  cc.  of  water. 

The  top  of  the  distilling  flask  was  closed  with  a  glass  stopper  packed  with 
asbestos,  and  the  side  arm  extended  into  a  Liebig  condenser  through  an 
asbestos  plug,  the  bromine  being  collected  in  a  flask  surrounded  with  ice 
water.  The  first  part  of  the  distillate  and  a  small  amount  of  bromine  re- 
maining in  the  distilling  flask  at  the  end  of  the  operation  were  discarded. 

The  distilling  flask  was  immersed  in  a  water  bath  kept  at  a  temperature 
slightly  above  the  boiling  point  of  bromine,  and  fine  capillary  tubes  sealed 
near  the  lower  ends  were  placed  within  the  flask  which  permited  the  bro- 
mine to  distil  without  bumping. 

The  bromine  prepared  according  to  the  above  method  was  tested  for 
presence  of  sulphates  according  to  Krauch-Merck,  76,  and  showed  no 
cloudiness  within  twelve  hours. 

(V)     Preparation  of  Sodium  Hypobromite. 

The  sodium  hypobromite  was  always  freshly  prepared  before  using. 
30  grams  of  sodium  hydroxide  purified  by  alcohol  were  dissolved  in  200 
cc.  of  water  and  5  cc.  of  the  purified  bromine  added  slowly  from  a  pipette. 

About  100  cc.  were  placed  in  each  of  the  absorption  tubes. 

(VI)     Blank  Experiment. 

Since  all  sodium  hydroxide  contains  traces  of  sulphur,  it  was  necessary 
to  determine  how  much  barium  sulphate  was  obtained  from  the  sodium 
hydroxide  alone  which  was  used  to  make  the  sodium  hypobromite. 

30  grams  of  sodium  hydroxide  purified  by  alcohol  were  dissolved  in 
water  and  bromine  added.  The  solution  was  then  neutralized  with 
hydrochloric  acid  and  carefully  evaporated  to  dryness,  the  last  stage  of 
which  was  done  on  a  water  bath,  and  then  heated  in  an  air  oven  for  two 
hours  at  120°. 

The  residue  in  the  beaker  after  cooling  was  dissolved  in  water  and 
the  solution  filtered  to  remove  any  silica.  The  filtrate  was  then  heated 
to  boiling  and  a  solution  of  barium  chloride  added. 


39 

The  average  of  three  trials  was  20  mg.  of  barium  sulphate  and  this 
correction  has  been  applied  in  Trials  6,  7,  and  8  in  Table  XII. 
(VII)     Results  in  Table  XL 

In  trials  1  to  12  inclusive  bromine  water  was  used  to  oxidize  the  sulphur 
dioxide,  while  in  trials  13  to  15  inclusive  alkaline  hypobromite  was  used. 

In  trials  1  to  10  inclusive,  elliptical  bulbed  absorption  tubes  were  used, 
while  in  trials  11  to  15  inclusive,  spherical  bulbed  absorption  tubes  were 
used. 

The  barium  sulphate  representing  the  sulphur  dioxide  was  always  low. 

In  order  to  see  if  any  of  the  sulphur  dioxide  was  going  through  the 
absorption  tubes  unoxidized,  two  changes  were  made: — 

(1)  Spherical  bulbed  absorption  tubes  were  substituted  for  the  ellip- 
tical bulbed  ones  in  order  to  increase  the  time  of  the  gas  through  the 
oxidizing  solution. 

(2)  The  alkaline  hypobromite  was  substituted  for  the  bromine  water, 
for,  if  any  of  the  sulphur  dioxide  were  converted  to  sulphur  trioxide  by 

TABLE  XI 
A.     Bromine  water  used"  in  elliptical  bulbed  absorption  tubes. 


Time  of 
boiling. 
Trial.     Hrs. 

Barium 
tetra- 
thion- 
ate 
used. 
Gm. 

BaSO4 
from 
direct  de-      BaSO4  from 
composition     oxidation 
of  Ba  tet.         of  SO2. 
Gm.                 Gm. 

BaS04 
from  ox- 
idation 
of  S. 
Gm. 

Ratios  found 
to  a  BaSO*  basis. 
BaS04:S02:S. 

1 

4 

1.0000 

0.2812 

0. 

2040 

0 

3239 

1 

.727: 

1.15 

2 

6 

5 

1.0000 

0.3258 

0 

2715 

0 

4105 

1 

.832: 

1.26 

3 

7 

75 

1.0000 

0.4113 

0 

3065 

0 

5211 

1 

.742: 

1.26 

4 

8 

3 

1.0000 

0.4734 

0 

4548 

0 

6573 

1 

.960: 

1.39 

5 

8 

1.0000 

0.4676 

0 

3916 

0 

6311 

1 

.837: 

1.349 

6 

8 

1  .  0000 

0.4146 

0 

3290 

0 

5850 

•« 

.796: 

1.418 

7 

7 

0  .  5000 

0.1435 

0 

1208 

0 

1297 

1 

.840: 

.903 

8 

9 

1.0000 

0.3350 

0 

2614 

0 

3422 

1 

.783: 

1S028 

9 

9 

1.0000 

0.3700 

0 

2746 

0 

4378 

1 

.746: 

1.189 

10 

7 

75 

1.0000 

0.3500 

0 

2685 

o 

3748 

1 

.767: 

1.067 

B. 

Bromine 

water  used  in  spherical 

bulbed  absorption 

tubes. 

11 

7 

75 

1.0000 

0.3347 

0 

2559 

0 

3750 

1:.765: 

1.118 

12 

8 

75 

1.0000 

0.3536 

0 

2692 

0 

4095 

1:.761: 

1.157 

C. 

Alkaline 

hypobromite  used 

in  spherical 

bulbed  absorption  tubes. 

13 

7 

75 

1.0000 

0.3569 

0 

3355 

0 

4171 

1:.940: 

1.168 

14  ' 

7 

1.0000 

0.5111 

0 

3518 

0 

7496 

1:.688: 

1.464 

15 

7 

5 

1.0000 

0.4160 

0.3136 

0 

5261 

1-..754: 

1.265 

40 

the  catalytic  action  of  the  carbon  dioxide  (Bigelow,  Zeitschr.  phys.  Chem., 
26,  531  (1898));  (Tithoff,  Zeitschr.  phys.  Chem.,  45,  679  (1903))  the  sulphur 
trioxide  would  be  retained  by  the  excess  of  sodium  hydroxide.  Further, 
the  excess  of  sodium  hydroxide  reacts  with  the  carbon  dioxide  reducing 
the  size  of  the  bubbles  of  gas  and  thus  increases  the  efficiency  of  oxidation. 

The  results  of  Table  XI  do  not  show  that  the  barium  tetrathionate 
solution  decomposes  according  to  the  equation 

BaS406  =  BaS04  +  SO2  +  2S 

The  barium  sulphate  was  chosen  as  the  basis  to  obtain  the  ratios  given 
since  it  was  the  least  variable. 

For  example,  the  ratios  of  Trial  15  were  obtained  as  shown  below,  while 
all  the  others  were  obtained  in  a  similar  way. 

.4160  ^  233.44  =  .001781  1.781  +•  1.781  =  1       BaSO4 

.0861  -^  64.07  =  .001344  1.344  -;-  1.781  =  .754    SO2 

.0723  -T-  32.07  =  .002253  2.253  -f-  1.781  =  1.265     S 

QUANTITATIVE    DECOMPOSITION    INCLUDING    THE    ANALYSIS    OF    THE 

FILTRATE 

As  already  stated,  the  results  given  in  Table  XI  do  not  show  that  barium 
tetrathionate  decomposes  from  a  boiling  solution  according  to  the  equa- 
tion given  above. 

Since  the  amounts  of  sulphur  dioxide  and  sulphur  were  always  low  and 
somewhat  variable,  it  seemed  possible  that  the  above  reaction  takes  place 
and  that  the  sulphur  dioxide  and  the  sulphur  react  with  the  thionate  in 
the  solution.  In  order  to  show  this,  it  was  necessary  to  analyze  the  nitrate 
obtained  after  filtering  off  the  barium  sulphate  and  sulphur  which  were  ob- 
tained by  boiling  the  barium  tetrathionate  solution. 

The  filtrate  was  analyzed  by  the  addition  of  liquid  bromine  to  the  solu- 
tion and  keeping  the  solution  warm  for  three  hours.  All  the  barium  was 
precipitated  as  barium  sulphate,  and  all  the  remaining  sulphur  was  oxi- 
dized to  sulphuric  acid.  The  excess  of  bromine  was  removed  by  boiling 
the  barium  sulphate  filtered  off  and  weighed,  and  the  sulphate  ion  pre- 
cipitated by  the  addition  of  a  solution  of  barium  chloride. 

The  headings  used  in  Table  XII  are  as  follows: — 

"BaSCU  From  Decomposition  of  Barium  Tetrathionate"  means  the 
total  barium  sulphate  obtained  by  boiling  the  barium  tetrathionate,  and 
includes  the  barium  sulphate  obtained  by  the  direct  decomposition,  the 


41 

barium  sulphate  from  the  sulphur  dioxide,  and  the  barium  sulphate  from 
the  sulphur. 

"BaSO4  From  Filtrate"  is  divided  into  two  parts,  for  when  oxidized 
with  the  bromine,  barium  sulphates  separated  out  directly  and  all  the 
remaining  sulphur  was  oxidized  to  sulphuric  acid. 

"BaSO4  Found  From  Same  Amount  of  Barium  Tetrathionate"  means 
that  the  same  weight  of  hydrous  barium  tetrathionate  was  taken  as  that 
used  in  the  decomposition  flask,  dissolved  in  water  in  a  beaker  and  oxi- 
dized with  bromine.  The  total  weight  of  barium  sulphate  obtained  in 
this  way  was  always  slightly  less  than  the  theoretical  calculated  from  the 
weight  of  hydrous  barium  tetrathionate  taken. 

Trial  1,  Table  XII,  was  the  same  decomposition  as  Trial  8  in  Table  XI; 
Trial  2  in  Table  XII  the  same  as  Trial  9  in  Table  XI  and  etc. 

TABLE  XII 
A.     Bromine  water  used  in  elliptical  bulbed  absorption  tubes. 

BaSO4  from  filtrate  Total  amt. 


Trial. 
1 

Barium 
tetra 
thionate 
used. 
Gm. 

1.0000 

BaS04              BaS04               BaSO4                                     of  BaSO< 
from                 from                  from                 Total           found  rom 
decomposi-          direct                all  re-               BaSOi           same  famt.            Error 
tion  of           decompo-          maining              found              of  Ba.                       in 
Ba.  Tet.             sition.             sulphur.                  in                   Tet.                   BaSOi. 
Gm.                   Gm.                   Gm.              analyses.            Gm.                     Gm. 

0.9386        0.2326         1.0500        2.2206        2.2976         -0.0770 

2 

1  .  0000 

1.0824        0.1972        0.9605        2.2401         2.2976 

-0.0575 

3 

1.0000 

0.9933        0.2276         1.0233        2.2447        2.2976 

-0.0529 

B.     Bromine  water  used  in  spherical  bulbed  absorption  tubes. 

4 

1.0000 

0.9656         0.2383         1.0442         2.2431         2.2976 

-0.0495 

5 

.1.0000 

1.0323        0.2279         1.0070        2.2672        2.2976 

-0.0304 

C.     Alkaline  hypobromite  used  in  spherical  bulbed  absorption 

tubes. 

6 

1  .  0000 

1.1095        0.2215         1.0185        2.3495        2.2976 

+0.0519 

7 

1  .  0000 

1.6135        00743        0.6722        2.3595        2.3208 

+0.0387 

8 

1.0000 

1.2557        0.1668        0.8714        2.2939        2.3208 

-0.0269 

The  results  in  Table  XII  show  that  the  loss  in  sulphur  dioxide  and  sul- 
phur in  the  boiling  solution  was  recovered  in  the  filtrate,  thus  proving  that 
secondary  reactions  occur  in  the  solution  during  the  boiling. 

Suppose  the  results  of  Trial  5  in  Table  XII  be  taken  (These  results 
were  from  the  filtrate  in  Trial  12  in  Table  XI). 

As  previously  stated,  when  the  filtrate  was  oxidized  by  liquid  bromine 
all  the  barium  was  precipitated  as  barium  sulphate  and  the  remaining 
sulphur  was  oxidized  to  sulphuric  acid.  If  the  barium  sulphate,  which 


42 

is  formed  directly  when  the  bromine  was  added  to  the  nitrate,  be  filtered 
from  the  sulphuric  acid  and  weighed,  it  is  possible  to  get  an  idea  of  the 
total  weight  of  barium  sulphate  that  should  be  obtained  from  the  nitrate. 

For  example: — if  all  the  barium  were  present  as  tetrathionate, 
0.2279  X  4  =  0.9116  gm.  of  barium  sulphate  which  should  be  found  from 

the  nitrate 

if  all  the  barium  were  present  as  pentathionate, 
.2279  X  5  =  1.1395  gm.  of  barium  sulphate  which  should  be  found  from 

the  nitrate. 
Whereas, 

.2279  +  1.0070  =  1.2349  gm.  of  barium  sulphate  actually  found  in  the 

filtrate. 

From  the  calculations  it  may  be  seen  that  the  weight  of  the  barium 
sulphate  actually  found  from  the  filtrate  may  be  accounted  for  by  the 
assumption  that  higher  thionates  than  the  tetrathionate  were  formed  in 
the  boiling  solution. 

If  the  presence  of  the  higher  thionates  be  assumed,  they  are  more  stable 
at  the  boiling  temperature  than  the  tetrathionate  which  is  certainly  not 
in  agreement  with  the  generally  accepted  Mendeleeff  (loc.  cit.)  structure. 

The  presence  of  colloidal  sulphur  will  not  explain  the  differences  found. 

CRYSTALLOGRAPHY  OF  SODIUM  AND  BARIUM  TETRATHIO- 

NATES 

BIBLIOGRAPHY 

No  reference  was  found  in  the  chemical  literature  where  any  crystallographic  study 
had  been  made  of  the  sodium  salt. 

Curtius,  Jour.f.  prak.  Ckem.,  N.  F.  24,  225,  (1881). 

Barium  tetrathionate  was  prepared  by  completely  neutralizing  Wackenroder's 
solution  with  barium  carbonate.  The  solution  was  analyzed  and  the  ratio  of  barium 
to  sulphur  was  found  to  be  about  1:4. 

The  salt  was  also  prepared  from  the  solution  by  the  addition  of  alcohol  and  crystals 
1/2  cm.  long  and  ll/i  mm.  wide  were  obtained.  The  crystals  were  dried  in  a  desiccator 
over  calcium  chloride. 

The  crystals  were  observed  through  the  polarizing  microscope  and  were  found  to 
be  rhombic  of  apparently  hemimorphic  habits  and  possessed  a  very  definite  cleavage 
parallel  to  the  macro  and  brachypinacoid. 

Shaw,  Jour.  Chem.  Soc.,  43,  351,  (1883). 

Potassium  tetrathionate  and  pentathionate  were  prepared  from  Wackenroder's 


43 

solution  by  neutralizing  with  potassium  hydroxide,  concentrating  on  a  water  bath,  and 
then  placed  in  a  vacuum  over  sulphuric  acid  and  fractionally  crystallized.  The  first 
and  second  crops  of  crystals  showed  the  ratio  of  potassium  to  sulphur  to  be  2:4;  the 
third,  fourth  and  fifth,  2:4.6;  the  sixth  (selected)  2:5. 

The  potassium  tetrathionate  crystals  when  examined  under  the  microscope  proved 
to  be  hemimorphic  forms  belonging  to  the  orthorhombic  system. 

Curtius  and  Henkel,  (loc.  cit.}. 

Barium  tetrathionate  was  prepared  as  previously  described.  It  had  a  fine  silvery 
texture  with  well  formed  crystal  plates.  When  the  crystals  were  examined  with  polar- 
ized light  they  were  found  to  be  monoclinic  in  nature  and  almost  always  twinned. 

Fock  and  Kluss,  Ber.,  2428,  (1890). 

Potassium  tetrathionate  was  prepared  by  the  gradual  addition  of  iodine  to  a  con- 
centrated solution  of  potassium  thiosulphate.  The  separated  salt  was  washed  free  of 
potassium  iodide  with  absolute  alcohol,  dissolved  in  warm  water,  filtered,  and  the  fil- 
trate treated  with  alcohol.  The  precipitate  consisted  of  large  glistening  tabular  crys- 
tals. 

The  salt  was  analyzed  by  oxidizing  a  known  amount  in  solution  with  bromine  water, 
and  precipitated  with  barium  chloride.  Also,  a  known  amount  of  the  salt  was  heated 
and  the  sulphate  determined.  These  analyses  show  the  salt  to  be  K^Oe. 

A  crystallographic  study  of  the  above  crystals  was  made  and  they  were  found  to 
be  identical  with  those  described  by  Rammelsberg  (Krys...  Phys.  Chem.  I,  495)  and  who 
gave  the  composition  of  the  crystalline  salt  as  KgSsOe.  (Rammelsberg's  salt  was  pre- 
pared from  Wackenroder's  solution). 

Potassium  tetrathionate  crystallizes  in  peculiar  hemimorphic  or  hemihedral  forms 
belonging  to  the  monoclinic  (monosymmetric)  system,  and  not  to  the  rhombic  system 
as  stated  by  Shaw  (loc.  cit.}. 

Potassium  pentathionate  was  prepared  according  to  the  method  of  Debus  (loc. 
cit.  294).  The  saH  on  analysis  proved  to  be  2K2S-A>.3H2O.  They  made  a  crystallo- 
graphic study  of  this  salt. 

EXPERIMENTAL 

(I)     Sodium  Tetrathionate. 

(1)  Crystallization   from   Absolute   Alcohol-Ether. 

The  crystals  were  obtained  by  adding  a  saturated  water  solution  of 
sodium  tetrathionate  at  50°  to  00°  to  an  absolute  alcohol-ether  mixture 
and  allowing  it  to  stand  for  twelve  hours.  The  crystals  thus  obtained 
were  very  small  and  occur  in  aggregate.  The  widths  of  the  crystal  aggre- 
gates varied  from  .000  mm.  to  .03  mm.,  while  the  widths  of  the  individual 
crystals  varied  from  .001  mm.  to  .01  mm.  The  lengths  of  the  aggregates 
and  individual  crystals  were  from  two  to  four  times  their  widths. 


44 


(2)  Crystallization  from  Water. 

The  crystals  were  obtained  from  a  saturated  water  solution  of  sodium 
tetrathionate  at  50°  to  60°  and  cooling  with  a  mixture  of  salt  and  ice  for 
about  two  hours;  they  were  much  larger  than  those  obtained  from  the 
absolute  alcohol-ether  solution  and  they  did  not  occur  in  aggregates. 

The  crystals  obtained  from  the  water  solution  varied  from  .06  mm.  to 
.3  mm.  in  width,  while  their  lengths  were  about  two  to  four  times  as  great. 

(3)  Optical  Characteristics  of  the  Crystals. 

The  crystals  obtained  from  the  water  solution  (See 
Fig.  3)  were  examined  under  the  polarizing  micro- 
scope and  the  following  results  obtained : — probably 
monoclinic ;  generally  twinned,  both  penetration  and 
contact,  sometimes  showing  a  more  or  less  hour  glass 
structure ;  the  crystals  show  on  the  side  pinacoid  the 
normal  emergence  of  Bxo  =  a;  the  acute  bisectrix  c 
is  almost  parallel  to  the  trace  of  one  of  the  small 
faces  which  is  inclined  at  an  angle  of  about  forty 
degrees  from  the  direction  of  elongation;  adjacent 
twins  have  a  difference  in  extinction  of  about  two  to 
four  degrees;  a  =  1.53  ±  .005;  c  =  1.65  =*=  .005; 
birefringence  =  .12  (high);  2  V  is  small,  about  ten 
to  twenty  degrees.  The  optical  sign  is  +.  The 
edges  of  the  crystals  were  somewhat  rounded  which 

prevented  accurate  measurement  of  angles  between  the  traces  of  crystal- 

lographic  faces. 

(II)     Barium   Tetrathionate. 

(1)  Crystallization  from  Absolute  Alcohol-Ether. 

The  crystals  from  the  absolute  alcohol-ether  mixture  were  obtained 
by  adding  a  saturated  water  solution  of  barium  tetrathionate  at  room  tem- 
perature to  an  absolute  alcohol-ether  mixture  and  allowing  to  stand  for 
twelve  hours.  The  crystals  were  rod  or  needle  shaped,  and  the  large  ones 
varied  in  width  from  .003  mm.  to  .007  mm.  and  in  length  from  .01  mm. 
to  .045  mm. 

(2)  Crystallization  from  Water. 

The  crystals  were  obtained  by  cooling  a  saturated  water  solution  of 
barium  tetrathionate  at  room  temperature  by  means  of  liquid  air.  The 


Fig.  3. — Highly  magni- 
fied twin  crystal  of 
Na2S4O6.2H2O  show- 
ing emergence  of 
Bxo  =  ft  on  side 
pinacoid. 


45 

dimensions  of  the  crystals  were  from  two  to  five  times  those  obtained  from 
the  absolute  alcohol-ether  mixture. 

(3)  Optical  Characteristics  of  Crystals. 

The  crystals  obtained  from  the  water  solution  were  examined  under 
the  polarizing  microscope  and  the  following  results  obtained: — rod  shaped, 
probably  monoclinic;  inclined  extinction,  angle  large,  30°;  crystals  in- 
variably twinned,  contact  and  frequently  poly  synthetically ;  elongation 
negative;  a  =  1.61  =»=  .005;  c  =  1.70  ±  .005;  birefringence  =  .09. 

ZINC  TETRATHIONATE 

BIBLIOGRAPHY 

Fordos  and  Gelis,  Ann.  chim.  phys.,  (3)  6,  492,  (1842). 
Jour.  /.  prak.  Chem.,  28,  478,  (1843). 

Zinc  tetrathionate  was  prepared  by  mixing  solutions  of  barium  tetrathionate  and 
zinc  sulphate  and  filtering.     They  further  state  that  the  zinc  tetrathionate  may  be 
obtained  from  the  solution  either  by  evaporation  or  by  the  addition  of  alcohol. 
Curtius,  Jour.f.  prak.  Chem.,  N.  F.  24,  237,  (1881). 

A  tetrathionate  of  zinc  was  prepared  from  Wackenroder's  solution  and  zinc  car- 
bonate. 

To  Wackenroder's  solution,  previoulsy  filtered  to  remove  sulphur,  freshly  pre- 
cipitated zinc  carbonate  was  added  to  neutralization.  To  this  a  volume  of  Wacken- 
roder's solution  equal  to  that  already  used  was  added  and  the  solution  filtered.  A 
small  amount  of  the  solution  was  boiled  in  a  small  tube  and  it  decomposed  explosively 
into  zinc  sulphate,  sulphur,  and  sulphur  dioxide. ' 

The  salt  was  obtained  from  the  solution  by  evaporating  to  a  syrupy  liquid  on  a 
water  bath  at  a  low  temperature  for  several  days,  then  placing  it  in  a  vacuum  and 
further  concentrating  to  a  crystalline  mass  which  was  separated  from  the  mother  liquor 
and  dried  between  filter  papers.     The  formula  of  the  salt  was  not  stated. 
Curtius  and  Henkel,  Jour.f.  prak.  Chem.,  N.  F.  37,  147,  (1888). 

Acid  tetrathionate  of  zinc  was  prepared  from  Wackenroder's  solution  and  zinc 
carbonate. 

A  definite  volume  of  clear  Wackenroder's  solution  was  neutralized  with  zinc  car- 
bonate, and  to  this  a  second  volume  of  Wackenroder's  solution  equal  to  the  first  was 
added.  The  solution  was  evaporated  in  a  vacuum  and  the  crystalline  residue  obtained 
separated  by  filtration,  and  recrystallized  from  absolute  alcohol  by  evaporation  in  a 
vacuum.  The  salt  was  dried  over  sulphuric  acid. 

Analysis: — A  definite  weight  of  the  salt  was  dissolved  in  water,  sodium  carbonate 
added,  and  chlorine  passed  through  the  solution.  The  zinc  was  determined  as  the  oxide. 
The  sulphur  was  precipitated  as  the  sulphate  by  the  addition  of  barium  chloride.  The 
water  of  crystallization  was  determined  by  combustion  with  lead  chromate.  The  analy- 
sis showed  the  salt  to  have  the  composition  Zn(HS4Oc)2- 


46 

PREPARATION 

(I)     Previous  Methods  Used. 

Zinc  tetrathionate  was  first  prepared  by  Fordos  and  Gelis  (loc.  tit.). 
The  general  methods  used  for  its  preparation  are  as  follows: — 

(1)  By  the  action  of  zinc  sulphate  on  barium  tetrathionate.     Fordos 
and  Gelis   (loc.  tit.). 

(2)  By  half  neutralizing  Wackenroder's  solution  with  zinc  carbonate. 
Curtius  (loc.  tit.);  Curtius  and  Henkel,  (loc.  tit.). 

The  salt  prepared  by  the  above  investigators  in  (2)  was  stated  to  be  the 
acid  salt  and  in  solution  reacted  strongly  acid. 

(II)     General  Procedure  of  Method  Used. 

Zinc  tetrathionate  was  prepared  in  solution  by  the  method  of  Fordos 
and  Gelis,  viz.  by  mixing  in  solution  equivalent  amounts  of  zinc  sulphate 
and  barium  tetrathionate,  and  filtering  off  the  barium  sulphate  formed. 

BaS4Oe.2H2O  and  ZnSO4.7H2O  were  weighed  out  in  such  equivalent 
amounts  as  to  have  1.0000  gm.  of  ZnS/Je  in  solution.  They  were  placed 
in  separate  beakers,  dissolved  in  small  amounts  of  water  and  the  zinc 
sulphate  solution  added  quantitatively  to  the  solution  of  barium  tetra- 
thionate and  allowed  to  stand  for  a  short  time.  It  was  then  filtered 
through  a  Gooch  into  a  test  tube  within  a  liter  Erlenmeyer  filtering  flask, 
using  a  little  suction.  This  solution  was  neutral  to  litmus. 

(Ill)     Preparation  of  Barium   Tetrathionate. 

The  barium  tetrathionate  was  prepared  according  to  the  "Suggested 
Method  under  'Barium  Tetrathionate.'  ' 

(IV)     Preparation  of  Zinc  Sulphate. 

Baker  and  Adamson's  C.  P.  zinc  sulphate  was  dissolved  in  warm  water 
at  about  35°  until  a  nearly  saturated  solution  was  obtained  and  then 
filtered.  The  filtrate  was  placed  in  a  crystallizing  dish  and  allowed  to 
cool,  during  which  some  of  the  salt  crystallized  out.  The  solution  was 
again  filtered,  the  crystallized  salt  being  discarded,  and  the  filtrate  placed 
in  a  crystallizing  dish,  seeded  with  a  small  amount  of  very  finely  pulverized 
zinc  sulphate  and  allowed  to  stand  for  several  days.  The  very  small 
crystals  which  formed  were  filtered  off,  dried  between  filter  paper  thor- 


47 

oughly  ground  in  a  mortar  and  placed  in  a  glass  stoppered  bottle.     The 
mother  liquor  was  discarded. 

QUALITATIVE  DECOMPOSITION 

1  gram  of  ZnS4O6  was  prepared  in  solution  as  previously  described  and 
transferred  to  an  Erlenmeyer  flask  in  such  a  way  that  there  were  100  cc. 
of  solution. 

The  Erlenmeyer  flask  was  attached  to  a  Liebig  condenser  and  the  solu- 
tion boiled  for  24  hours,  carbon  dioxide  being  passed  through  the  solution 
during  the  entire  time.  Considerable  sulphur  collected  in  the  condenser 
during  the  process. 

The  odor  of  sulphur  dioxide  was  easily  detected  at  the  mouth  of  the 
condenser.  The  evolved  gas  was  passed  into  bromine  water,  the  excess 
of  bromine  boiled  off,  a  few  drops  of  hydrochloric  acid  added  and  then 
a  solution  of  barium  chloride.  A  white  precipitate  was  formed. 

Negative  results  were  obtained  for  hydrogen  sulphide  when  tested  for 
with  lead  acetate. 

At  the  end  of  the  boiling  the  residue  in  the  condenser  was  added  to  the 
flask,  the  solution  filtered,  and  the  residue  and  filtrate  tested  qualitatively. 

(I)     Residue. 
It  was  found  to  consist  of  sulphur,  sulphide  being  absent. 

(II)     Filtrate. 

(1)  Sulphate: — The  solution  was  tested  in  the  usual  way  and  found 
present. 

(2)  Thiosulphate:— 

(a)  Tested  with  a  solution  of  ammonium  molybdate  and  concen- 
trated sulphuric  acid.     Blue  ring  immediately. 

(b)  Tested  with  iodine  solution.     1  drop  of  N/10  iodine  was  de- 
colorized by  10  cc.  of  the  solution;  two  drops  gave  an  iodine  color. 

(c)  Tested   with   a   dilute   solution   of   potassium   permanganate. 
The  solution  was  bleached. 

(3)  Sulphite: — The    sodium   nitroprusside-potassium   ferrocyanide-zinc 
sulphate  tested  gave  a  negative  result. 

(4)  Trithionate: — The    mercuric    chloride,    potassium    permanganate, 
mercurous  nitrate,  and  hydrochloric  acid  tests  were  applied.     Definite 
results  were  not  obtained,  but  if  present  it  was  in  very  small  amounts. 


48 

(5)  Pentathionate. 

(a)  Tested   with   ammoniacal   silver   nitrate.     Immediate   brown 
precipitate. 

(b)  Tested  with  concentrated  potassium  hydroxide.     Cloudiness 
which  does  not  disappear  when  made  slightly  acid  with  hydrochloric  acid. 

(c)  Tested   with   mercurous   nitrate.     Black   precipitate   at   first, 
but  on  further  addition  of  the  mercurous  nitrate  the  precipitate  became 
yellow. 

From  the  results  of  the  tests  given  above  it  may  be  concluded  that  the 
following  are  the  final  products  of  decomposition  in  a  boiling  solution  of 
zinc  tetrathionate : — sulphate,  sulphur  dioxide,  sulphur  and  some  penta- 
thionate;  also  a  small  amount  of  thiosulphate. 

QUANTITATIVE  DECOMPOSITION 

(I)  Descriptive. 

The  apparatus  used,  the  time  of  boiling,  and  the  passing  of  the  carbon 
dioxide,  were  the  same  as  under  barium. 

The  absorption  tubes  for  the  sulphur  dioxide  were  spherical  bulbed; 
alkaline  hypobromite,  which  was  prepared  as  previously  described  under 
barium,  was  used  as  the  oxidizing  agent. 

(II)  Procedure. 

1.0000  gm.  of  zinc  tetrathionate  was  prepared  in  solution  as  described 
under  "General  Procedure  of  Method  Used,"  transferred  quantitatively 
to  the  Erlenmeyer  decomposition  flask  in  such  a  way  that  the  total  volume 
of  water  used  was  100  cc. 

At  the  end  of  the  boiling  the  sulphur  which  had  collected  in  the  condenser 
was  removed  to  the  decomposition  flask,  and  the  solution  filtered  through 
a  hard  filter  using  all  necessary  precautions. 

(1)  The  Residue. 

The  residue  on  the  filter  was  washed  into  a  beaker  and  oxidized  by  addi- 
tion of  bromine  using  the  precautions  to  obtain  and  oxidize  all  the  sulphur. 
After  the  removal  of  the  excess  of  bromine,  the  sulphate  ion  was  precipi- 
tated by  the  addition  of  a  solution  of  barium  chloride  using  .the  necessary 
precautions,  and  the  barium  sulphate  obtained  is  designated  in  the  tabel 
as  "BaSO4  From  Oxidation  of  Sulphur." 

(2)  The  Filtrate. 

The  filtrate  obtained  after  the  removal  of  sulphur  was  heated  nearly 


49 

to  boiling  and  a  solution  of  barium  chloride  used,  thus  precipitating  the 
sulphate  ions  present.  The  barium  sulphate  formed  was  filtered  off 
and  is  designated  in  the  table  as  "BaSO4  From  Zinc  Sulphate." 

The  contamination  due  to  the  presence  of  zinc  ions  as  determined  by 
dissolving  the  barium  sulphate  in  hot  concentrated  sulphuric  acid  and 
reprecipitating  by  diluting  with  water  amounted  to  only  about  1  mg.  and 
in  most  of  the  determinations  has  been  neglected. 

(3)  Sulphur  Dioxide. 

Sulphur  dioxide  was  determined  exactly  as  described  under  barium. 

The  sulphur  content  of  the  sodium  hydroxide  as  found  in  the  blank 
experiment  under  barium  has  been  applied  in  each  determination. 

TABLE  XIII 


Trial. 

Time  of 
boiling 
hrs. 

Zinc  tet- 
rathionate 
used. 
Gm. 

BaSO4 
from 
zinc 
sulphate 
Gm. 

BaSO4  from 
oxidation 
of  sulphur 
.dioxide. 
Gm. 

BaS04 
from 
oxidation 
of  sulphur. 
Gm. 

Ratios  found  to 
ZnSO4  basis 
ZnS04:S02:S. 

1 

8 

1.0000 

0.2426 

0.1216 

0.2248 

1:  .501:  .927 

2 

8 

1.0000 

0.2399 

0.1925 

0.1811 

1:.  802:.  755 

3 

9.5 

1.0000 

0.2344 

0.2020 

0.2067 

1:.860:  .881 

4 

8 

1.0000 

0.2862 

0.2372 

0  .  2302 

1:  .828:.  803 

5 

8 

1.0000 

0.2478 

0.1987 

0.1520 

1:.  800:.  613 

The  ratios  obtained  above  do  not  show  that  zinc  tetrathionate  in  solu- 
tion decomposes  quantitatively  into  zinc  sulphate,  sulphur  dioxide,  and 
two  atoms  of  sulphur. 

The  ratios  given  in  the  above  table  were  obtained  in  exactly  the  same 
way  as  under  Barium  in  Table  XI,  except  the  "Barium  Sulphate  From 
the  Zinc  Sulphate"  has  been  converted  to  an  equivalent  amount  of  zinc 
sulphate. 

QUANTITATIVE  DECOMPOSITION  INCLUDING  THE  ANALYSIS  OF  FILTRATES 

As  in  the  case  of  barium,  the  boiled  solution  after  the  removal  of  the 
sulphur  and  the  sulphate  ions  was  oxidized  with  bromine,  the  excess  of 
bromine  boiled  off  and  a  solution  of  barium  chloride  added  observing  the 
necessary  precautions. 

The  headings  in  Table  XIV  are  as  follows: 

"BaSO4  From  Decomposition  of  Zinc  Tetrathionate"  means,  after  the 
solution  of  zinc  tetrathionate  has  been  boiled,  it  is  the  total  barium  sul- 
phate obtained  from  the  zinc  sulphate,  plus  that  obtained  from  the  oxi- 
dized sulphur  dioxide,  plus  that  from  the  oxidized  sulphur. 


50 

"BaSO4  From  Filtrate"  means  the  final  filtrate  which  was  oxidized  with 
bromine  and  precipitated  with  a  solution  of  barium  chloride  in  the  usual 
way. 

"Total  Amount  of  BaSC>4  From  Same  Amount  of  Zinc  Tetrathionate" 
means  that  1.0000  gm.  of  zinc  tetrathionate  was  prepared  in  solution, 
using  the  same  samples  and  the  same  amounts  of  barium  tetrathionate 
and  zinc  sulphate  as  were  used  to  prepare  the  zinc  tetrathionate  in  the 
decomposition  flask,  oxidized  by  bromine  and  precipitated  by  a  solution 
of  barium  chloride  observing  precautions  previously  stated. 

TABLE  XIV 


BaSO4  from 
decomposi- 

BaSO4 

Total 
BaSO4 

Total  amt. 
of  BaSOi 

Zinc  tetra- 

tion of 

from 

found 

from  same 

Error 

Time  of 

thionate 

zinc  tetra- 

ni- 

in an- 

weight 

in 

boiling. 

used. 

thionate. 

trate. 

alyses. 

of  zinc  tetia- 

BaSO4. 

Trial. 

hrs. 

Gm. 

Gm. 

Gm. 

Gm. 

thionate.  Gm. 

Gm. 

1 

8 

1.0000 

0  .  5890 

2.5013 

3.0903 

3  .  0386 

+0.0517 

2 

9.5 

1.0000 

0.6431 

2.4404 

3.0835 

3  .  0386 

+0.0449 

3 

8 

1.0000 

0.7536 

2.2458 

2.9994 

3.0755 

-0.0761 

4 

8 

1.0000 

0.5985 

2.4325 

3.0310 

3.0755 

-0.0445 

The  results  of  Table  XIV  show  that  the  loss  of  sulphur  dioxide  and 
sulphur  in  the  decomposition  of  the  zinc  tetrathionate  by  boiling  was 
recovered  in  the  filtrate. 

The  ratio  of  zinc  sulphate  to  sulphur  dioxide  in  Table  XIII  is  about  the 
same  as  barium  sulphate  to  sulphur  dioxide  in  Table  XI,  while  the  ratio 
of  zinc  sulphate  to  sulphur  in  Table  XIII  is  less  than  that  of  barium  sul- 
phate to  sulphur  in  Table  XI. 

If  there  was  good  evidence  of  the  formation  of  pentathionate  and  quite 
probably  hexathionate  when  the  barium  tetrathionate  solution  was  boiled, 
there  is  stronger  evidence  that  the  higher  thionates  were  formed  when 
the  zinc  tetrathionate  solution  was  boiled,  because  there  was  a  propor- 
tionately greater  loss  of  sulphur  from  the  boiling  solution. 

NICKEL  TETRATHIONATE 

BIBLIOGRAPHY 

Kessler,  Jour.  f.  prak.  Chem.,  loc.  cit.,  36. 

Pogg.  Ann.  Phys.  Chem.,  loc.  cit.,  256. 

"Nickel  tetrathionate  was  prepared  by  mixing  equivalent  solutions  of  nickel  sul- 
phate and  lead  tetrathionate  and  evaporating  in  a  vacuum.  The  salt  was  very  deli- 
quescent and  its  solution  was  practically  as  stable  as  solutions  of  tetrathionic  acid." 

The  analysis  of  the  salt  was  not  given. 


51 

PREPARATION 

(I)     General  Procedure  of  Method  Used. 

Nickel  tetrathionate  was  prepared  in  solution  in  a  way  similar  to  that 
used  in  the  case  of  the  zinc. 

2.000-gm.  of  BaS4O6.2H2O  and  1.322  gm.  of  NiSO4.6H2O  were  weighed 
out,  placed  in  separate  beakers  and  each  dissolved  in  a  small  amount  of 
water.  The  nickel  sulphate  solution  was  then  transferred  quantitatively 
to  the  barium  tetrathionate  solution,  allowed  to  stand  a  short  time  and 
filtered  exactly  as  under  zinc. 

The  solution  had  a  light  green  color  and  was  neutral  to  litmus. 
(II)     The  Barium  Tetrathionate  and  Nickel  Sulphate  Used. 

The  same  sample  of  barium  tetrathionate  was  used  as  in  the  case  of  zinc. 

Ordinary  C.   P.  hydrous  nickel  sulphate  was  used. 

QUALITATIVE  DECOMPOSITION 

The  nickel  tetrathionate  solution  was  prepared  as  described  and  trans- 
ferred to  the  Erlenmeyer  decomposition  flask  so  that  there  were  100  cc. 
of  water  used.  The  apparatus  and  procedure  were  the  same  as  described 
under  zinc. 

The  solution  was  boiled  for  24  hours  and  during  this  time  the  color 
remained  a  light  green,  thus  showing  that  hydrogen  sulphide  was  not 
evolved  and  nickel  sulphide  formed. 

During  the  boiling,  sulphur  dioxide  was  given  off  and  sulphur  collected 
in  the  condenser.  At  the  end  of  the  boiling  the  sulphur  in  the  condenser 
was  removed  to  the  decomposition  flask  and  the  solution  filtered. 

(I)  Residue. 
The  residue  proved  to  be  sulphur. 

(II)  Filtrate. 

Tests  were  made  for  sulphate,  thiosulphate,  sulphite,  trithionate,  and 
pentathionate  and  the  results  show  the  final  products  in  the  decomposition 
of  a  boiling  solution  of  zinc  tetrathionate  are: — sulphate,  sulphur  dioxide, 
and  sulphur;  some  pentathionate  and  a  small  amount  of  thiosulphate. 

CONCLUSIONS 

Sodium  Tetrathionate. 
(1)  Sodium   tetrathionate   was   prepared   by   several   similar  methods 


52 

and  the  salt  crystallized  from  water  solution  by  cooling  had  the  highest 
degree  of  purity. 

(2)  The   salt   crystallized  from  water   solution   had   the   composition 
Na2S4O6.2H2O. 

(3)  The  yield  was  considerably  increased  by  preparing  the  salt  according 
to  the  "Suggested  Method." 

(4)  The   dissociation   pressure   of   the   hydrous   sodium   tetrathionate 
is  of  such  magnitude  that  the  salt  should  not  be  dried  over  concentrated 
sulphuric  acid  for  any  considerable  time. 

Barium  Tetrathionate. 

(1)  Barium  tetrathionate  was  prepared  and  on  analysis  proved  to  be 
quite  pure,  and  that  crystallized  from  a  water  solution  had  the  highest 
degree  of  purity. 

(2)  Practically  all  the  details  of  the  method  for  its  preparation  were 
worked  out. 

(3)  Barium  tetrathionate  slowly  decomposes  at  the  ordinary  tempera- 
ture. 

(4)  Qualitative  decomposition  of  \  boiling  solution  showed  that  the 
final  products  were  sulphate,  sulphur  dioxide,  and  sulphur  together  with 
pentathionate  and  a  trace  of  thiosulphate. 

(5)  Quantitative  decomposition  of  the  boiling  solution  showed  that 
secondary  reactions  occur  in  the  solution  forming  higher  thionates. 

CRYSTALLOGRAPHIC  STUDY  OF  SODIUM  AND  BARIUM  TETRATHIONATE 

(1)  Crystals  of  both  sodium  and  barium  tetrathionates  were  prepared 
from  a  water  solution  and  some  of  their  optical  characteristics  determined. 

Zinc  Tetrathionate 

(1)  A  solution  of  zinc  tetrathionate  was  prepared  and  it  was  neutral 
to  litmus. 

(2)  Qualitative  decomposition  of  the  boiling  solution  showed  that  the 
final  products  were  sulphate,  sulphur  dioxide,  sulphur  and  some  penta- 
thionate together  with  small  amount  of  thiosulphate. 

(3)  Quantitative  analysis  of  the  boiling  solution  showed  that  secondary 
reactions  occur  and  that  higher  thionates  were  formed  to  a  greater  extent 
than  in  the  case  of  barium. 


53 

Nickel  Tetrathionate 

(1)  A  solution  of  nickel  tetrathionate  was  prepared;  it  had  a  light  green 
color  and  was  neutral  to  litmus. 

(2)  Qualitative  decomposition  of  the  boiling  solution  showed  that  the 
final  products  were  sulphate,  sulphur  dioxide,  sulphur  and  some  penta- 
thionate  together  with  a  small  amount  of  thiosulphate. 


ACKNOWLEDGMENT 

The  writer  desires  to  express  his  sincere  thanks  to  Dr.  Wm.  E.  Henderson 
under  whose  supervision  this  work  was  done,  and  whose  advice  was  most 
helpful  at  all  times  and  whose  interest  was  inspiring. 

Further,  the  authors  desire  to  thank  Dr.  Wm.  J.  McCaughey,  Head  of 
the  Department  of  Mineralogy  in  Ohio  State  University,  for  most  valuable 
assistance  in  determining  the  crystallographic  data. 


HBH 


YD  0*893 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


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